Solve 5x*x=90

$$5x \times x=90$$

Solve for x

$$x=3\sqrt{2}\approx 4.242640687$$

$$x=-3\sqrt{2}\approx -4.242640687$$

Steps by Finding Square Root

Multiply x and x to get x^{2}.

$$5x^{2}=90$$

Divide both sides by 5.

$$x^{2}=\frac{90}{5}$$

Divide 90 by 5 to get 18.

$$x^{2}=18$$

Take the square root of both sides of the equation.

$$x=3\sqrt{2} x=-3\sqrt{2}$$

Steps Using the Quadratic Formula

Multiply x and x to get x^{2}.

$$5x^{2}=90$$

Subtract 90 from both sides.

$$5x^{2}-90=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 5 for a, 0 for b, and -90 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\times 5\left(-90\right)}}{2\times 5}$$

Square 0.

$$x=\frac{0±\sqrt{-4\times 5\left(-90\right)}}{2\times 5}$$

Multiply -4 times 5.

$$x=\frac{0±\sqrt{-20\left(-90\right)}}{2\times 5}$$

Multiply -20 times -90.

$$x=\frac{0±\sqrt{1800}}{2\times 5}$$

Take the square root of 1800.

$$x=\frac{0±30\sqrt{2}}{2\times 5}$$

Multiply 2 times 5.

$$x=\frac{0±30\sqrt{2}}{10}$$

Now solve the equation x=\frac{0±30\sqrt{2}}{10} when ± is plus.

$$x=3\sqrt{2}$$

Now solve the equation x=\frac{0±30\sqrt{2}}{10} when ± is minus.

$$x=-3\sqrt{2}$$

The equation is now solved.

$$x=3\sqrt{2} x=-3\sqrt{2}$$