Question

Factorise x2-x-72
Please answer this question. ​

Answer 1

Answer:

(x + 8) (x - 9)

Step-by-step explanation:

1. Multiply the first term and the third term:

x2 *(- 72) =  -72x2

Try to divide it into two parts such that when added together, it becomes x

-72x2 = +8x, -9x.

When multiplied together, it equals -72x2

When added together, it becomes x.

2. Replace 'x' with these two terms.

x2 + 8x - 9x - 72

3. Factorise using grouping method (given in textbook):

x (x + 8) - 9 (x + 8)

(x + 8) (x - 9)

Hope this helps! :)