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

Jul 18, 2016

-23

#### Explanation:

By substituting the given numeric values for x,y and z into the expression.

That is

${\left(3\right)}^{3} - 2 {\left(5\right)}^{2} - 3 {\left(3\right)}^{3} + {\left(- 3\right)}^{4}$
$\text{------------------------------------------------}$
I'll evaluate each term separately.

${\left(3\right)}^{3} = 3 \times 3 \times 3 = 9 \times 3 = 27$

$2 {\left(5\right)}^{2} = 2 \times \left(5 \times 5\right) = 2 \times 25 = 50$

$3 {\left(3\right)}^{3} = 3 \times \left(3 \times 3 \times 3\right) = 3 \times 27 = 81$

${\left(- 3\right)}^{4} = \left[\left(- 3\right) \times \left(- 3\right)\right] \times \left[\left(- 3\right) \times \left(- 3\right)\right] = 9 \times 9 = 81$
$\text{-------------------------------------------------}$
Replace these values back into the expression , noting the values which are subtracted.

$\Rightarrow 27 - 50 - \cancel{81} + \cancel{81} = 27 - 50 = - 23$