Question

URGENT CLASS 9 PLEASE HELP​

Answer 1

Answer:

The factorisation is = 3(4x² + 18x + 5)(x² + 9x - 1)

Step-by-step explanation:

Here, 12(x² + 7x)² - 3(x² + 7x)(2x - 1) - 15(2x - 1)²

Here, firstly take  a = (x² + 7x)

                            b = (2x - 1)

=> 12a² - 3ab - 15b²

We can factorise this by middle term splitting method

The product of first and third term is (12a²)(-15b²) = - 180a²b²

We can split the middle term -3ab into - 15ab and 12ab whose product is same as that of first term and third term .

=>  12a² - 15ab + 12ab - 15b²

=>  12a² + 12ab - 15ab - 15b²

=>  12a(a + b) -15b(a + b)

=> (12a - 15b)(a + b)

Substituting   a = (x² + 7x)

                      b = (2x - 1)

=>   (12a - 15b)(a + b)

=>   [12(x² + 7x) -15(2x - 1)](x² + 7x + 2x - 1)

=> [12x² + 84x - 30x + 15](x² + 9x - 1)

=>  [12x² + 54x + 15](x² + 9x - 1)

=>  3[4x² + 18x + 5](x² + 9x - 1)

Thus, the factors are -  3[4x² + 18x + 5](x² + 9x - 1)