# How do you evaluate 3x^2-4y^2 if x=5 and y=3?

Jun 7, 2017

The answer is $39$.

#### Explanation:

$3 {x}^{2} - 4 {y}^{2}$

Then we substitute the given $x$ and $y$ values into the expression:

$3 {\left(5\right)}^{2} - 4 {\left(3\right)}^{2}$

Now, according to the order of operations, we simplify the exponential powers first, thus, reducing the expression to this:

$3 \left(25\right) - 4 \left(9\right)$

Then, we use the order of operations again and do the multiplication next:

$75 - 36$

We then use the order of operations a final time and finish off the expression with subtraction:

$39$