Question

factorise : x²-12x-45​

Answer 1

Answer:

x² - 12x - 45

• (x - 15) (x + 3)

• X - 15

= X1 = 15

• X + 3

= X2 = -3

why 15 and -3?

if you 'times', the result should be -45.

if you 'plus', the result should be -12.

and the end, -15 moved expand to right. due to moving, a minus turned into a plus. Likewise the number 3.

sorry for my english