Solve 2x^2+kx-15=0text{is}x=3

$$2 x ^ { 2 } + k x - 15 = 0 \text { is } x = 3$$

Solve for x, k

$$x=3$$

$$k=-1$$

Solution Steps

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

$$2\times 3^{2}+k\times 3-15=0$$

Calculate 3 to the power of 2 and get 9.

$$2\times 9+k\times 3-15=0$$

Multiply 2 and 9 to get 18.

$$18+k\times 3-15=0$$

Subtract 15 from 18 to get 3.

$$3+k\times 3=0$$

Subtract 3 from both sides. Anything subtracted from zero gives its negation.

$$k\times 3=-3$$

Divide both sides by 3.

$$k=\frac{-3}{3}$$

Divide -3 by 3 to get -1.

$$k=-1$$

The system is now solved.

$$x=3 k=-1$$