Answer :
With [tex]f(x)=-10x+9[/tex], we have
[tex]f(x+h) = -10(x+h) + 9 = -10x + 9 - 10h[/tex]
Then the difference quotient is
[tex]\dfrac{f(x+h)-f(x)}h = \dfrac{(-10x+9-10h)-(-10x+9)}h = \dfrac{-10h}h = -10[/tex]
since h ≠ 0.
With [tex]f(x)=-10x+9[/tex], we have
[tex]f(x+h) = -10(x+h) + 9 = -10x + 9 - 10h[/tex]
Then the difference quotient is
[tex]\dfrac{f(x+h)-f(x)}h = \dfrac{(-10x+9-10h)-(-10x+9)}h = \dfrac{-10h}h = -10[/tex]
since h ≠ 0.