Question

USE THE IDENTITY
(x + a)(x + b) = {x }^{2} + (a + b)x + ab(x+a)(x+b)=x2+(a+b)x+ab
TO FIND THE FOLLOWING PRODUCTS.

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Answer 1

Answer:

1st

$9 {x}^{2} + 6ax - 15bx - 10ab$

2nd

$4 {a}^{2} - 16ab + 15 {b}^{2}$

Answer 2

Answer:

$using \: \: (x + a)(x + b) = {x}^{2} + (a + b)x + ab \\ \\ (i) \: \: a = 2a \: \: and \: \: b = - 5b \\ \\ x \: \: - > 3x \\ \\ = > 9 {x}^{2} + (2a - 5b)(3x) - 10ab \\ \\ (ii) \: \: a = - 5b \: \: and \: \: b = - 3b \\ \\ x \: \: \: - > \: \: 2a \\ \\ = > 4 {a}^{2} - 16ab + 15 {b}^{2} = 0$