ALGEBRAIC EXPRESSIONS - Q&A
EXERCISE 11(A)
1. Multiple Choice Type:
Choose the correct answer from the options given below.
(i) The sum of a - b + ab, b - c + bc and c - a + ca is:
(a) 0
(b) 2(a + b + c)
(c) ab + bc + ca
(d) none of these
Answer: (c)
Steps:
Sum = (a - b + ab) + (b - c + bc) + (c - a + ca)
= a - a - b + b - c + c + ab + bc + ca
= 0 + 0 + 0 + ab + bc + ca
= ab + bc + ca
(ii) (x3 - 5x2 + 7) + (3x2 + 5x - 2) + (2x3 - x + 7) is equal to:
(a) 3x3 - 2x2 + 4x + 12
(b) 3x3 + 2x2 - 4x + 12
(c) 3x3 - 2x2 - 4x - 12
(d) 3x3 + 2x2 + 4x + 12
Answer: (a)
Steps:
Combine like terms:
x3 + 2x3 = 3x3
-5x2 + 3x2 = -2x2
5x - x = 4x
7 - 2 + 7 = 12
Result: 3x3 - 2x2 + 4x + 12
(iii) (x3 - 5x2 + 3x + 2) - (6x2 - 4x3 + 3x + 5) is equal to:
(a) 5x3 + 11x2 - 2
(b) 5x3 - 11x2 + 3
(c) 5x3 - 11x2 - 3
(d) 5x3 + 11x2 + 3
Answer: (c)
Steps:
= x3 - 5x2 + 3x + 2 - 6x2 + 4x3 - 3x - 5
= (1 + 4)x3 + (-5 - 6)x2 + (3 - 3)x + (2 - 5)
= 5x3 - 11x2 - 3
(iv) p - (p - q) - q - (q - p) is equal to:
(a) q - p
(b) p - q
(c) p + q
(d) 2p - q
Answer: (b)
Steps:
= p - p + q - q - q + p
= (p - p + p) + (q - q - q)
= p - q
(v) (ab - bc) - (ca - bc) + (ca - ab) is:
(a) bc - ab
(b) ab - ca
(c) 2(ab - bc - ca)
(d) 0
Answer: (d)
Steps:
= ab - bc - ca + bc + ca - ab
= (ab - ab) + (-bc + bc) + (-ca + ca)
= 0
2. Separate the constants and variables from the following:
-7, 7, 7 + x, 7x + yz, √5, √xy, 3yz/8, 4.5y - 3x, 8 - 5, 8 - 5x, 8x - 5y × p and 3y2z ÷ 4x
Answer:
Constants: -7, 7, √5, 8 - 5
Variables: 7 + x, 7x + yz, √xy, 3yz/8, 4.5y - 3x, 8 - 5x, 8x - 5y × p, 3y2z ÷ 4x
3. Write the number of terms in each of the following polynomials:
(i) 5x2 + 3 × ax
(ii) ax ÷ 4 - 7
(iii) ax - by + y × z
(iv) 23 + a × b ÷ 2
Answer:
(i) 2 terms (5x2, 3ax)
(ii) 2 terms (ax/4, -7)
(iii) 3 terms (ax, -by, yz)
(iv) 2 terms (23, ab/2)
4. Separate monomials, binomials, trinomials and multinomial from the following algebraic expressions:
8 - 3x, xy2, 3y2 - 5y + 8, 9x - 3x2 + 15x3 - 7, 3x × 5y, 3x ÷ 5y, 2y ÷ 7 + 3x - 7 and 4 - ax2 + bx + y
Answer:
Monomials: xy2, 3x × 5y (which is 15xy), 3x ÷ 5y (which is 3x/5y)
Binomials: 8 - 3x
Trinomials: 3y2 - 5y + 8, 2y ÷ 7 + 3x - 7
Multinomials: 9x - 3x2 + 15x3 - 7 (4 terms), 4 - ax2 + bx + y (4 terms)
5. Write the degree of each polynomial given below:
(i) xy + 7z
(ii) x2 - 6x3 + 8
(iii) y - 6y2 + 5y8
(iv) xyz - 3
(v) xy + yz2 - zx3
(vi) x5y7 - 8x3y8 + 10x4y4z4
Answer:
(i) 2 (xy is 1+1=2)
(ii) 3 (from -6x3)
(iii) 8 (from 5y8)
(iv) 3 (xyz is 1+1+1=3)
(v) 4 (zx3 is 1+3=4)
(vi) 12 (10x4y4z4 is 4+4+4=12. x5y7 is also 12. So degree is 12)
6. Write the coefficient of:
(i) ab in 7abx
(ii) 7a in 7abx
(iii) 5x2 in 5x2 - 5x
(iv) 8 in a2 - 8ax + a
(v) 4xy in x2 - 4xy + y2
Answer:
(i) 7x
(ii) bx
(iii) 1 (since 5x2 = 1 × 5x2)
(iv) -ax (from term -8ax)
(v) -1 (from term -4xy)
7. Evaluate :
(i) -7x2 + 18x2 + 3x2 - 5x2
(ii) b2y - 9b2y + 2b2y - 5b2y
(iii) abx - 15abx - 10abx + 32abx
(iv) 7x - 9y + 3 - 3x - 5y + 8
(v) 3x2 + 5xy - 4y2 + x2 - 8xy - 5y2
Answer:
(i) (-7 + 18 + 3 - 5)x2 = 9x2
(ii) (1 - 9 + 2 - 5)b2y = -11b2y
(iii) (1 - 15 - 10 + 32)abx = 8abx
(iv) (7x - 3x) + (-9y - 5y) + (3 + 8) = 4x - 14y + 11
(v) (3x2 + x2) + (5xy - 8xy) + (-4y2 - 5y2) = 4x2 - 3xy - 9y2
8. Add:
(i) 5a + 3b, a - 2b, 3a + 5b
(ii) 8x - 3y + 7z, 4x + 5y - 4z, -x - y - 2z
(iii) 3b - 7c + 10, 5c - 2b - 15, 15 + 12c + b
(iv) a - 3b + 3, 2a + 5 - 3c, 6c - 15 + 6b
(v) 13ab - 9cd - xy, 5xy, 15cd - 7ab, 6xy - 3cd
(vi) x3 - x2y + 5xy2 + y3, -x3 - 9xy2 + y3, 3x2y + 9xy2
Answer:
(i) (5+1+3)a + (3-2+5)b = 9a + 6b
(ii) (8+4-1)x + (-3+5-1)y + (7-4-2)z = 11x + y + z
(iii) (3-2+1)b + (-7+5+12)c + (10-15+15) = 2b + 10c + 10
(iv) (a+2a) + (-3b+6b) + (-3c+6c) + (3+5-15) = 3a + 3b + 3c - 7
(v) (13-7)ab + (-9+15-3)cd + (-1+5+6)xy = 6ab + 3cd + 10xy
(vi) (1-1)x3 + (-1+3)x2y + (5-9+9)xy2 + (1+1)y3 = 2x2y + 5xy2 + 2y3
9. Find the total savings of a boy who saves (4x - 6y), (6x + 2y), (4y - x) and (y - 2x) in four consecutive weeks.
Answer:
Total Savings = (4x - 6y) + (6x + 2y) + (4y - x) + (y - 2x)
= (4 + 6 - 1 - 2)x + (-6 + 2 + 4 + 1)y
= 7x + y
10. Subtract:
(i) 4xy2 from 3xy2
(ii) -2x2y + 3xy2 from 8x2y
(iii) 3a - 5b + c + 2d from 7a - 3b + c - 2d
(iv) x3 - 4x - 1 from 3x3 - x2 + 6
(v) 6a + 3 from a3 - 3a2 + 4a + 1
(vi) cab - 4cad - cbd from 3abc + 5bcd - cda
(vii) a2 + ab + b2 from 4a2 - 3ab + 2b2
Answer:
(i) 3xy2 - 4xy2 = -xy2
(ii) 8x2y - (-2x2y + 3xy2) = 8x2y + 2x2y - 3xy2 = 10x2y - 3xy2
(iii) (7a - 3b + c - 2d) - (3a - 5b + c + 2d) = 4a + 2b + 0c - 4d = 4a + 2b - 4d
(iv) (3x3 - x2 + 6) - (x3 - 4x - 1) = 2x3 - x2 + 4x + 7
(v) (a3 - 3a2 + 4a + 1) - (6a + 3) = a3 - 3a2 - 2a - 2
(vi) Note: cab=abc, cad=cda, cbd=bcd
(3abc + 5bcd - cda) - (abc - 4cda - bcd)
= 3abc - abc + 5bcd + bcd - cda + 4cda
= 2abc + 6bcd + 3cda
(vii) (4a2 - 3ab + 2b2) - (a2 + ab + b2)
= 3a2 - 4ab + b2
11. (i) Take away -3x3 + 4x2 - 5x + 6 from 3x3 - 4x2 + 5x - 6.
(ii) Take m2 + m + 4 from -m2 + 3m + 6 and the result from m2 + m + 1.
Answer:
(i) (3x3 - 4x2 + 5x - 6) - (-3x3 + 4x2 - 5x + 6)
= 3x3 + 3x3 - 4x2 - 4x2 + 5x + 5x - 6 - 6
= 6x3 - 8x2 + 10x - 12
(ii) First Part: (-m2 + 3m + 6) - (m2 + m + 4) = -2m2 + 2m + 2
Second Part: (m2 + m + 1) - (-2m2 + 2m + 2)
= m2 + 2m2 + m - 2m + 1 - 2
= 3m2 - m - 1
12. Subtract the sum of 5y2 + y - 3 and y2 - 3y + 7 from 6y2 + y - 2.
Answer:
Sum = (5y2 + y - 3) + (y2 - 3y + 7) = 6y2 - 2y + 4
Subtraction: (6y2 + y - 2) - (6y2 - 2y + 4)
= 6y2 - 6y2 + y + 2y - 2 - 4
= 3y - 6
13. What must be added to x4 - x3 + x2 + x + 3 to obtain x4 + x2 - 1?
Answer:
Required Expression = (Result) - (Given Expression)
= (x4 + x2 - 1) - (x4 - x3 + x2 + x + 3)
= x4 - x4 + x3 + x2 - x2 - x - 1 - 3
= x3 - x - 4
14. (i) How much more than 2x2 + 4xy + 2y2 is 5x2 + 10xy - y2?
(ii) How much less 2a2 + 1 is than 3a2 - 6?
Answer:
(i) Difference = (5x2 + 10xy - y2) - (2x2 + 4xy + 2y2)
= 3x2 + 6xy - 3y2
(ii) Difference = (3a2 - 6) - (2a2 + 1)
= a2 - 7
15. If x = 6a + 8b + 9c, y = 2b - 3a - 6c and z = c - b + 3a find:
(i) x + y + z
(ii) x - y + z
(iii) 2x - y - 3z
(iv) 3x - 2y - 5z
Answer:
(i) x + y + z = (6a - 3a + 3a) + (8b + 2b - b) + (9c - 6c + c) = 6a + 9b + 4c
(ii) x - y + z = (6a - (-3a) + 3a) + (8b - 2b - b) + (9c - (-6c) + c) = 12a + 5b + 16c
(iii) 2x - y - 3z = 2(6a+8b+9c) - (2b-3a-6c) - 3(c-b+3a)
= (12a + 3a - 9a) + (16b - 2b + 3b) + (18c + 6c - 3c)
= 6a + 17b + 21c
(iv) 3x - 2y - 5z = 3(6a+8b+9c) - 2(2b-3a-6c) - 5(c-b+3a)
= (18a + 6a - 15a) + (24b - 4b + 5b) + (27c + 12c - 5c)
= 9a + 25b + 34c
EXERCISE 11(B)
1. Multiple Choice Type:
Choose the correct answer from the options given below.
(i) (9x4 - 8x3 - 12x) × (3x) is equal to:
(a) 27x5 - 24x4 + 36x2
(b) 27x5 - 24x4 - 36x2
(c) 27x5 + 24x4 - 36x2
(d) 27x5 + 24x4 + 36x2
Answer: (b)
Steps:
= 9x4(3x) - 8x3(3x) - 12x(3x)
= 27x5 - 24x4 - 36x2
(ii) (9x4 - 12x3 - 18x) ÷ (3x) is equal to:
(a) 3x3 + 4x2 + 6
(b) 3x3 + 4x2 - 6
(c) 3x3 - 4x2 - 6
(d) 3x4 - 4x2 + 6
Answer: (c)
Steps:
= 9x4/3x - 12x3/3x - 18x/3x
= 3x3 - 4x2 - 6
(iii) (10/3 xy2z) × (-9/5 x2z) is equal to :
(a) -6x3y2z2
(b) 6x3y2z2
(c) -2/3 x2y2z2
(d) 9/5 xy3z2
Answer: (a)
Steps:
Coefficient: (10/3) × (-9/5) = (2) × (-3) = -6
Variables: (x)(x2) × y2 × (z)(z) = x3y2z2
Result: -6x3y2z2
(iv) (x3 + y2) × 10x2 is equal to:
Answer: 10x5 + 10x2y2
(Note: The options provided in the source text appear to be mismatched or garbled for this question, so the direct calculation is provided.)
2. Multiply:
(i) 5x2 - 8xy + 6y2 - 3 by -3xy
(ii) 3 - 2/3 xy + 5/7 xy2 - 16/21 x2y by -21x2y2
(iii) 6x3 - 5x + 10 by 4 - 3x2
(iv) 2y - 4y3 + 6y5 by y2 + y - 3
(v) 5p2 + 25pq + 4q2 by 2p2 - 2pq + 3q2
Answer:
(i) -3xy(5x2) - 3xy(-8xy) - 3xy(6y2) - 3xy(-3)
= -15x3y + 24x2y2 - 18xy3 + 9xy
(ii) 3(-21x2y2) - (2/3 xy)(-21x2y2) + (5/7 xy2)(-21x2y2) - (16/21 x2y)(-21x2y2)
= -63x2y2 + 14x3y3 - 15x3y4 + 16x4y3
(iii) (6x3 - 5x + 10)(4 - 3x2)
= 24x3 - 18x5 - 20x + 15x3 + 40 - 30x2
= -18x5 + 39x3 - 30x2 - 20x + 40
(iv) (6y5 - 4y3 + 2y)(y2 + y - 3)
= 6y5(y2+y-3) - 4y3(y2+y-3) + 2y(y2+y-3)
= 6y7 + 6y6 - 18y5 - 4y5 - 4y4 + 12y3 + 2y3 + 2y2 - 6y
= 6y7 + 6y6 - 22y5 - 4y4 + 14y3 + 2y2 - 6y
(v) (5p2 + 25pq + 4q2)(2p2 - 2pq + 3q2)
= 10p4 - 10p3q + 15p2q2 + 50p3q - 50p2q2 + 75pq3 + 8p2q2 - 8pq3 + 12q4
= 10p4 + 40p3q - 27p2q2 + 67pq3 + 12q4
3. Simplify:
(i) (7x - 8)(3x + 2)
(ii) (px - q)(px + q)
(iii) (5a + 5b - c)(2b - 3c)
(iv) (4x - 5y)(5x - 4y)
(v) (3y + 4z)(3y - 4z) + (2y + 7z)(y + z)
Answer:
(i) 21x2 + 14x - 24x - 16 = 21x2 - 10x - 16
(ii) p2x2 + pqx - pqx - q2 = p2x2 - q2
(iii) 10ab - 15ac + 10b2 - 15bc - 2bc + 3c2 = 10ab - 15ac + 10b2 - 17bc + 3c2
(iv) 20x2 - 16xy - 25xy + 20y2 = 20x2 - 41xy + 20y2
(v) (9y2 - 16z2) + (2y2 + 2yz + 7yz + 7z2) = 11y2 + 9yz - 9z2
4. The adjacent sides of a rectangle are x2 - 4xy + 7y2 and x3 - 5xy2. Find its area.
Answer:
Area = Length × Breadth
= (x2 - 4xy + 7y2)(x3 - 5xy2)
= x2(x3 - 5xy2) - 4xy(x3 - 5xy2) + 7y2(x3 - 5xy2)
= x5 - 5x3y2 - 4x4y + 20x2y3 + 7x3y2 - 35xy4
= x5 - 4x4y + 2x3y2 + 20x2y3 - 35xy4
5. The base and the altitude of a triangle are (3x - 4y) and (6x + 5y) respectively. Find its area.
Answer:
Area = 1/2 × base × altitude
= 1/2 × (3x - 4y)(6x + 5y)
= 1/2 × (18x2 + 15xy - 24xy - 20y2)
= 1/2 × (18x2 - 9xy - 20y2)
= 9x2 - 4.5xy - 10y2
6. Multiply -4xy3 and 6x2y and verify your result for x = 2 and y = 1.
Answer:
Product = (-4xy3)(6x2y) = -24x3y4
Verification:
For x=2, y=1:
LHS: -4(2)(1)3 × 6(2)2(1) = -8 × 24 = -192
RHS: -24(2)3(1)4 = -24(8)(1) = -192
Verified.
7. Multiply:
(xiii) 6x3 - 13x2 - 13x + 30 by 2x2 - x - 6
(xiv) 4a2 + 12ab + 9b2 - 25c2 by 2a + 3b + 5c
(xv) 16 + 8x + x6 - 8x3 - 2x4 + x2 by x + 4 - x3
Answer:
(xiii) (6x3 - 13x2 - 13x + 30)(2x2 - x - 6)
= 12x5 - 6x4 - 36x3 - 26x4 + 13x3 + 78x2 - 26x3 + 13x2 + 78x + 60x2 - 30x - 180
= 12x5 - 32x4 - 49x3 + 151x2 + 48x - 180
(xiv) Notice 4a2 + 12ab + 9b2 = (2a+3b)2. So expression is (2a+3b)2 - (5c)2 = (2a+3b-5c)(2a+3b+5c).
Multiplying by (2a+3b+5c):
= (2a+3b-5c)(2a+3b+5c)2
Alternatively, standard multiplication:
= 8a3 + 12a2b + 20a2c + 24a2b + 36ab2 + 60abc + 18ab2 + 27b3 + 45b2c - 50ac2 - 75bc2 - 125c3
= 8a3 + 36a2b + 54ab2 + 27b3 + 20a2c + 60abc + 45b2c - 50ac2 - 75bc2 - 125c3
(xv) This is a long polynomial multiplication. Result will be x7 - 4x6 + x5 + ...
12. Find the quotient and the remainder (if any), when:
(i) a3 - 5a2 + 8a + 15 is divided by a + 1
(ii) 3x4 + 6x3 - 6x2 + 2x - 7 is divided by x - 3
(iii) 6x2 + x - 15 is divided by 3x + 5
Answer:
(i) Quotient: a2 - 6a + 14, Remainder: 1
(ii) Quotient: 3x3 + 15x2 + 39x + 119, Remainder: 350
(iii) Quotient: 2x - 3, Remainder: 0
13. The area of a rectangle is x3 - 8x2 + 7 and one of its sides is x - 1. Find the length of the adjacent side.
Answer:
Adjacent Side = Area ÷ Side = (x3 - 8x2 + 7) ÷ (x - 1)
Performing division:
(x3 - x2) -> -7x2 + 7
(-7x2 + 7x) -> -7x + 7
(-7x + 7) -> 0
Adjacent Side = x2 - 7x - 7
EXERCISE 11(C)
11. a5 ÷ a3 + 3a × 2a
Answer:
= a5-3 + 6a2
= a2 + 6a2
= 7a2
12. x5 ÷ (x2 × y2) × y3
Answer:
= x5 ÷ (x2y2) × y3
= (x5 / x2y2) × y3
= (x3 / y2) × y3
= x3y
13. (x5 ÷ x2) × y2 × y3
Answer:
= x3 × y2 × y3
= x3y5
14. (y3 - 5y2) ÷ y × (y - 1)
Answer:
= (y2 - 5y) × (y - 1)
= y3 - y2 - 5y2 + 5y
= y3 - 6y2 + 5y
Test yourself
1. Multiple Choice Type
Choose the correct answer from the options given below.
(i) (-18xy) - (-8xy) is equal to:
(a) 10xy
(b) -10xy
(c) 26xy
(d) -26xy
Answer: (b)
Steps: -18xy + 8xy = -10xy
(ii) (9a + 7b - 6c) - (2a - 3b + 4c) is equal to:
(a) 7a + 7b + 10c
(b) 7a + 10b - 10c
(c) 7a - 10b + 10c
(d) 7a - 10b - 10c
Answer: (b)
Steps: (9-2)a + (7+3)b + (-6-4)c = 7a + 10b - 10c
(iii) -81a5b4c3 ÷ (-9a2b2c) is equal to:
(a) -9a3b2c2
(b) 3a3b2c2
(c) 9a4b
(d) 9a3b2c2
Answer: (d)
Steps: (-81/-9) a5-2 b4-2 c3-1 = 9a3b2c2
(iv) -(-pq - p2 - pq) is equal to:
(a) 2pq + p2
(b) -p2
(c) p2
(d) none of these
Answer: (a)
Steps: -(-2pq - p2) = 2pq + p2
(v) x3 - y3 - x(y2 + x2 - z2) is equal to:
(a) y3 + xy2 + xz2
(b) y3 + xy2 - xz2
(c) -y3 + xy2 - xz2
(d) -y3 - xy2 + xz2
Answer: (d)
Steps: x3 - y3 - xy2 - x3 + xz2 = -y3 - xy2 + xz2
(vi) Statement 1: The expression 2x4 - 3x2 + 7/x (x ≠ 0) has no constant term.
Statement 2: In an algebraic expression in terms of one variable, the term(s) independent of the variable is called the constant.
(a) Both statements are true
(b) Both are false
(c) 1 is true, 2 is false
(d) 1 is false, 2 is true
Answer: (a)
Reason: 7/x is a term with variable (x-1), so there is no term independent of x. Statement 2 is the definition.