Question

Factorise:. (ii) X²-2X-15​

Answer 1

Answer:

To Factorise : x

2

+2x−15

By splitting the middle term

=x

2

+5x−3x−15

=x(x+5)−3(x+5)

=(x−3)(x+5)

So, x

2

+2x−15=(x−3)(x+5)

Answer 2

The first term is, x2 its coefficient is 1 .

The middle term is, -2x its coefficient is -2 .

The last term, "the constant", is -15

Step-1 : Multiply the coefficient of the first term by the constant 1 • -15 = -15

Step-2 : Find two factors of -15 whose sum equals the coefficient of the middle term, which is -2 .

-15 + 1 = -14

-5 + 3 = -2 That's it

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -5 and 3

x2 - 5x + 3x - 15

Step-4 : Add up the first 2 terms, pulling out like factors :

x • (x-5)

Add up the last 2 terms, pulling out common factors :

3 • (x-5)

Step-5 : Add up the four terms of step 4 :

(x+3) • (x-5)

Which is the desired factorization