Answer:
x= -7, x=8
Step-by-step explanation:
factoring method..
f (x) = - x² + 12x - 20
= - x² + 10x + 2x - 20
= - x( x - 10 ) + 2( x - 10 )
= ( x - 10 ) ( -x + 2 )
=> x = 10, x = 2
