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 $15.6$

Since $f\left(x\right)=2x^2$

Therefore,

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

$=\frac{2(4+3.8)(4-3.8)}{4-3.8}=2(4+3.8)=2\times 7.8=15.6$