(x-5)(x+8)
Let's factor
x
2
+
3
x
−
40
x
2
+
3
x
−
40
The middle number is 3 and the last number is -40.
Factoring means we want something like
(x+_)(x+_)
Which numbers go in the blanks?
We need two numbers that...
Add together to get 3
Multiply together to get -40
Can you think of the two numbers?
Try -5 and 8:
-5+8 = 3
-5*8 = -40
Fill in the blanks in
(x+_)(x+_)
with -5 and 8 to get...
(x-5)(x+8)