# If x=2, y= -5, and z= -1, then what does (x-y) (x+y-z) equal?

Apr 19, 2018

$\left(x - y\right) \left(x + y - z\right) = \left(2 + 5\right) \times \left(2 - 5 + 1\right) = 7 \times \left(- 2\right) = - 14$

#### Explanation:

First, substitute the values of $x$, $y$, and $z$.

$\left(x - y\right) \left(x + y - z\right) = \left[2 - \left(- 5\right)\right] \left[2 + \left(- 5\right) - \left(- 1\right)\right]$

Next, we remove unnecessary addition and subtraction signs to complete the expression.

• $- \mathmr{and} + = -$
• $- \mathmr{and} - = +$
• $+ \mathmr{and} + = +$

So

$\left(2 + 5\right) \left(2 - 5 + 1\right)$

Next, we complete the expressions inside the brackets (order of operations).

$\left(7\right) \times \left(- 2\right)$

Finally, to complete the expression, we carry out the multiplication:

$- 14$