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