Question

If the value of $x=-2$ , $y=3$ , $z=1$ , then find the value of the following :

$x^2+2xy-z^2$

Answer 1

Given that :

$x=-2$ , $y=3$ , $z=1$

And we have to find the value of the expression :

$x^2+2xy-z^2$

Finding the value of the expression at the given values of variables :

So

$$\begin{gathered} x^2+2xy-z^2={\left(-2\right)}^2+2\left(-2\right)\left(3\right)-{\left(1\right)}^2 \\ =4+2\left(-6\right)-1 \\ =4-12-1 \\ =4-13 \\ =-9 \end{gathered}$$

Therefore value of the given expression at $x=-2$ , $y=3$ , $z=1$ is :

$x^2+2xy-z^2=-9$