Chapter 1, Problem 17CT

To determine

To calculate: the value of expression $2(r^2-15)$ when $r=4$ .

Answer to Problem 17CT

The value of expression $2(r^2-15)$ is $2$ when $r=4$ .

Explanation of Solution

Given information : consider, the expression provided in the question,

  $2(r^2-15)$ .

Calculation : to evaluate the expression, it is needed to substitute r by 4then square the 4 after that subtract 15 from result then multiply 2 by result.

$\begin{array}{l}2(r^2-15)=2(4^2-15)\\ 2(r^2-15)=2(16-15)\\ 2(r^2-15)=2(1)\\ 2(r^2-15)=2\end{array}$ [square, subtract and multiply]

Hence,

Thus, The value of expression $2(r^2-15)$ is $2$ when $r=4$ .