Question

Factorise 4(a + b)2 – 28(ab) + 49b2

Answer 1

Answer:

25a

2

−4b

2

−28bc−49c

2

=(5a)

2

−(2b)

2

+28bc−(7c)

2

=(5a)

2

−{(2b)

2

+2×2b×7c−(7c)

2

}

∵[(a+b)

2

=a

2

+b

2

+2ab]

=(5a)

2

−(2b+7c)

2

∵[a

2

−b

2

=(a−b)(a+b)]

={(5a)−(2b+7c)}{(5a)+(2b+7c)}

=(5a−2b−7c)(5a+2b+7c)