CPM Homework Help : CCA Problem A-10

The word “evaluate” has many different meanings. In algebra, when you are asked to evaluate an expression for a specified value of the variable(s), you are being asked to find the value of the expression. You do this by replacing a variable with a number and calculating the result. For example, if you are asked to evaluate the expression $4x−2$ when $x=−7$ , you would put $-7$ in place of the variable and then calculate: $4·(−7)−2=−30$ .

Evaluate the expressions below for the given values of $x$ and $y$ .

Step 1:

Rewrite the expression with the number in place of the variable and simplify if possible.

$\frac{6}{x}+9\text{ if }x=3$
Hint (a):
$\frac{6}{(3)}+9=2+9$
Answer (a):
$11$

$8x − 3 + y \text{ if } x = 2 \text{ and } y = 1$
Hint (b):
$8\left(2\right) − 3 + \left(1\right)$

$2xy \text{ if } x = 5 \text{ and } y = −3$
Hint (c):
$2\left(5\right)\left(−3\right) = 10\left(−3\right)$
Answer (c):
$−30$

$2x^2−y\text{ if }x=3\text{ and }y=8$
Hint (d):
$2\left(3\right)^{2} − \left(8\right)$