Answer:
f(x+h)-f(x)/h=5h+10x-6
Explanation:
f(x)=5x²-6x+1
f( x+h )=5( x+h )²-6(x+h)+1
=5(x²+h²+2hx)-6x-6h+1
=5x²+5h²+10xh-6x-6h+1
f(x+h)-f(x)=(5x²+5h²+10xh-6x-6h+1-(5x²-6x+1)
=5x²+5h²+10xh-6x-6h+1-5x²+6x-1
=5h²+10hx-6h
f(x+h)-f(x)/h=(5h²+10hx-6h)/h
=5h+10x-6