X2 - 8x + 15 = 0

quadratic formula

The quadratic formula is x = (-b+-sqrt (b^2-4 (a) (c))) / 2a

Using the quadratic formula, we get:

x = ( - (-8) + -sqrt ((-8) ^2-4 (15) (1))) / 2 (1)

x = (8+-sqrt (64-60)) / 2

x = (8+-sqrt (4)) / 2

x = (8+-2) / 2

x=10/2 and x=6/2

x=5 and x=3

We could do it way faster by completing the square:

x^2-8x+15=0

(x-5) (x-3) = 0

x=5 and x=3

Hope both methods make sense! BTW, the + - thing means add or subtract