Solve {l}{x=-2}{y=4}{z={(7x^2-xy)}{(-6y+x^2)}}{text{Solvefor}atext{where}}{a=z}

$$\left. \begin{array} { l } { x = -2 }\\ { y = 4 }\\ { z = {(7 x ^ {2} - x y)} {(-6 y + x ^ {2})} }\\ { \text{Solve for } a \text{ where} } \\ { a = z } \end{array} \right.$$

Solve for x, y, z, a

$$a=-720$$

Solution Steps

Consider the third equation. Insert the known values of variables into the equation.

$$z=\left(7\left(-2\right)^{2}-\left(-2\times 4\right)\right)\left(-6\times 4+\left(-2\right)^{2}\right)$$

Calculate -2 to the power of 2 and get 4.

$$z=\left(7\times 4-\left(-2\times 4\right)\right)\left(-6\times 4+\left(-2\right)^{2}\right)$$

Multiply 7 and 4 to get 28.

$$z=\left(28-\left(-2\times 4\right)\right)\left(-6\times 4+\left(-2\right)^{2}\right)$$

Multiply -1 and -2 to get 2.

$$z=\left(28+2\times 4\right)\left(-6\times 4+\left(-2\right)^{2}\right)$$

Multiply 2 and 4 to get 8.

$$z=\left(28+8\right)\left(-6\times 4+\left(-2\right)^{2}\right)$$

Add 28 and 8 to get 36.

$$z=36\left(-6\times 4+\left(-2\right)^{2}\right)$$

Multiply -6 and 4 to get -24.

$$z=36\left(-24+\left(-2\right)^{2}\right)$$

Calculate -2 to the power of 2 and get 4.

$$z=36\left(-24+4\right)$$

Add -24 and 4 to get -20.

$$z=36\left(-20\right)$$

Multiply 36 and -20 to get -720.

$$z=-720$$

Consider the fourth equation. Insert the known values of variables into the equation.

$$a=-720$$

The system is now solved.

$$x=-2 y=4 z=-720 a=-720$$