Which of the following is a factor of x2 − 8x + 15?

(x−3)(x−5)

Step-by-step explanation:

Let's factor x2−8x+15

x2−8x+15

The middle number is -8 and the last number is 15.

Factoring means we want something like

(x+_)(x+_)

Which numbers go in the blanks?

We need two numbers that...

Add together to get -8

Multiply together to get 15

Can you think of the two numbers?

Try -3 and -5:

-3+-5 = -8

-3*-5 = 15

Fill in the blanks in

(x+_)(x+_)

with -3 and -5 to get...

(x-3)(x-5)

24

step-by-step explanation:

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15