tolong bantu jawab no brp aja pake cara

8. f(x) = x²-6x-16
f¹(x) = 2x-6
2x-6>0
2x>6
x>3

9. f(x) =2x²-16x+8
f¹(x) = 4x-16
4x-16<0
4x<16
x<4

10. f(x) = x²+24x-15
f¹(x) = 2x+24
2x+24<0
2x<-24
x<-12