Factor the following polynomials by grouping :
Question 1 :
x3 - 2x2 - x + 2
Question 2 :
x3 + 3x2 - x - 3
Question 3 :
x3 + x2 - 4x - 4
Question 4 :
x3 - 3x2 + 2x - 6
Question 5 :
x4 - x3 - x + x2
Question 6 :
x8 - x4 - x2 + 1
Question 7 :
5a - 5b - xa + xb
Question 8 :
2xy - 4x - 3ay + 6a
1. Answer :
= x3 - 2x2 - x + 2
= (x3 - 2x2) + (-x + 2)
= x2(x - 2) - 1(x - 2)
= (x2 - 1)(x - 2)
= (x2 - 12)(x - 2)
Using algebraic identity a2 - b2 = (a + b)(a -b),
= (x + 1)(x - 1)(x - 2)
2. Answer :
= x3 + 3x2 - x - 3
= (x3 + 3x2) + (-x - 3)
= x2(x + 3) - 1(x + 3)
= (x2 - 1)(x + 3)
= (x2 - 12)(x + 3)
Using algebraic identity a2 - b2 = (a + b)(a -b),
= (x + 1)(x - 1)(x + 3)
3. Answer :
= x3 + x2 - 4x - 4
= (x3 + x2) + (-4x - 4)
= x2(x + 1) - 4(x - 1)
= (x2 - 4)(x + 1)
= (x2 - 22)(x + 1)
Using algebraic identity a2 - b2 = (a + b)(a -b),
= (x + 2)(x - 2)(x + 1)
4. Answer :
= x3 - 3x2 + 2x - 6
= (x3 - 3x2) + (2x - 6)
= x2(x - 3) + 2(x - 3)
= (x2 + 2)(x - 3)
5. Answer :
= x4 - x3 - x + x2
Arrange the terms with powers in descending order.
= x4 - x3 + x2 - x
= (x4 - x3) + (x2 - x)
= x3(x - 1) + x(x - 1)
= (x3 + x)(x - 1)
= x(x2 + 1)(x - 1)
6. Answer :
= x8 - x4 + x2 + 1
= (x8 - x4) + (x2 + 1)
= x4(x4 - 1) + 1(x2 + 1)
= x4(x4 - 1) + 1(x2 + 1)
= x4[(x2)2 - 12] + 1(x2 + 1)
= x4(x2 - 1)(x2 + 1) + 1(x2 + 1)
= (x2 + 1)[x4(x2 - 1) + 1]
7. Answer :
= 5a - 5b - xa + xb
= (5a - 5b) + (-xa + xb)
= 5(a - b) - x(a - b)
= (a - b)(5 - x)
8. Answer :
= 2xy - 4x - 3ay + 6a
= (2xy - 4x) + (-3ay + 6a)
= 2x(y - 2) - 3a(y - 2)
= (2x - 3a)(y - 2)
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