Chapter 7.1, Problem 51CCR

To determine

Evaluate the expression $-4st$ if $s=-9,t=3$ .

Answer to Problem 51CCR

  $108$

Explanation of Solution

Given information:

The expression is $-4st$ if $s=-9,t=3$ .

Concept Used:

Rules of Addition/ Subtraction:

• Two numbers with similar sign always get added and the resulting number will carry the similar sign.
• Two numbers with opposite signs always get subtracted and the resulting number will carry the sign of larger number.

Rules of Multiplication/ Division:

• The product/quotient of two similar sign numbers is always positive.
• The product/quotient of two numbers with opposite signs is always negative.

Calculation:

In order to evaluate the expression $-4st$ , first putting the value of $s=-9,t=3$ and then solving it as shown below:

  $\begin{array}{l}-4st=-4\cdot \left(-9\right)\cdot \left(3\right)\\ =108\end{array}$

Thus, the value of the expression is 108.