Solve 4x*5x=80

$$4x \times 5x=80$$

Solve for x

$$x=2$$

$$x=-2$$

Steps by Finding Square Root

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

$$4x^{2}\times 5=80$$

Multiply 4 and 5 to get 20.

$$20x^{2}=80$$

Divide both sides by 20.

$$x^{2}=\frac{80}{20}$$

Divide 80 by 20 to get 4.

$$x^{2}=4$$

Take the square root of both sides of the equation.

$$x=2 x=-2$$

Steps Using the Quadratic Formula

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

$$4x^{2}\times 5=80$$

Multiply 4 and 5 to get 20.

$$20x^{2}=80$$

Subtract 80 from both sides.

$$20x^{2}-80=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 20 for a, 0 for b, and -80 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\times 20\left(-80\right)}}{2\times 20}$$

Square 0.

$$x=\frac{0±\sqrt{-4\times 20\left(-80\right)}}{2\times 20}$$

Multiply -4 times 20.

$$x=\frac{0±\sqrt{-80\left(-80\right)}}{2\times 20}$$

Multiply -80 times -80.

$$x=\frac{0±\sqrt{6400}}{2\times 20}$$

Take the square root of 6400.

$$x=\frac{0±80}{2\times 20}$$

Multiply 2 times 20.

$$x=\frac{0±80}{40}$$

Now solve the equation x=\frac{0±80}{40} when ± is plus. Divide 80 by 40.

$$x=2$$

Now solve the equation x=\frac{0±80}{40} when ± is minus. Divide -80 by 40.

$$x=-2$$

The equation is now solved.

$$x=2 x=-2$$