Question

The sides of a rectangle are (6 - x) cm and (x - 3) cm. If its area is maximum then x =

• A. $4$
• B. $4.5$
• C. $4.8$
• D. $6$

Answer 1

The correct option is B $4.5$

area of rectangle $=(6-x)(x-3)$
$\frac{d\left(area\right)}{dx}=-(x-3)+(6-x)$
$0=-2x+9$
$x=4-5$