Answer:
should be 9
Step-by-step explanation:
what
A
x=7
20
16=1 2/10R + -8
16+8= 12/10R
24=12/10R
R=20
C
5ax²-20x³+2a-8x
=5 x²(a-4x)+2(a-4x)
=(a-4x)(5x²+2)