Question

A function is given. Determine the average rate of change of the function between the given values of the variable: f(x)= 4x^2; x=3, x=3+h

Answer 1

$\bf slope = {{ m}}= \cfrac{rise}{run} \implies \cfrac{{{ f(x_2)}}-{{ f(x_1)}}}{{{ x_2}}-{{ x_1}}}\impliedby \begin{array}{llll} average\ rate\\ of\ change \end{array}\\\\ -------------------------------$

$\bf f(x)= 4x^2 \qquad \begin{cases} x_1=3\\ x_2=3+h \end{cases}\implies \cfrac{f(3+h)-f(3)}{(3+h)~-~(3)} \\\\\\ \cfrac{[4(3+h)^2]~~-~~[4(3)^2]}{\underline{3}+h-\underline{3}}\implies \cfrac{4(3^2+6h+h^2)~~-~~4(9)}{h} \\\\\\ \cfrac{4(9+6h+h^2)~~-~~36}{h}\implies \cfrac{\underline{36}+24h+4h^2~~\underline{-~~36}}{h} \\\\\\ \cfrac{24h+4h^2}{h}\implies \cfrac{\underline{h}(24+4h)}{\underline{h}}\implies 24+4h$