Question

If $f\left(x\right)=2x^2,$ find $\frac{f\left(3.8\right)-f\left(4\right)}{3.8-4}$

• A. $1.56$
• B. $156$
• C. $15.6$
• D. $0.156$

Answer 1

The correct option is C $15.6$

$\frac{f\left(3.8\right)-f\left(4\right)}{3.8-4}$
$=\frac{2\times (3.8{)}^2-2\times (4{)}^2}{3.8-4}$
$=\frac{2({3.8}^2-4^2)}{(3.8-4)}$
$=\frac{2(3.8+4)(3.8-4)}{(3.8-4)}$
$=2(3.8+4)=15.6$