Solve 7x*3x=21

$$7x \times 3x=21$$

Solve for x

$$x=1$$

$$x=-1$$

Steps by Finding Square Root

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

$$7x^{2}\times 3=21$$

Multiply 7 and 3 to get 21.

$$21x^{2}=21$$

Divide both sides by 21.

$$x^{2}=\frac{21}{21}$$

Divide 21 by 21 to get 1.

$$x^{2}=1$$

Take the square root of both sides of the equation.

$$x=1 x=-1$$

Steps Using the Quadratic Formula

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

$$7x^{2}\times 3=21$$

Multiply 7 and 3 to get 21.

$$21x^{2}=21$$

Subtract 21 from both sides.

$$21x^{2}-21=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 21 for a, 0 for b, and -21 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\times 21\left(-21\right)}}{2\times 21}$$

Square 0.

$$x=\frac{0±\sqrt{-4\times 21\left(-21\right)}}{2\times 21}$$

Multiply -4 times 21.

$$x=\frac{0±\sqrt{-84\left(-21\right)}}{2\times 21}$$

Multiply -84 times -21.

$$x=\frac{0±\sqrt{1764}}{2\times 21}$$

Take the square root of 1764.

$$x=\frac{0±42}{2\times 21}$$

Multiply 2 times 21.

$$x=\frac{0±42}{42}$$

Now solve the equation x=\frac{0±42}{42} when ± is plus. Divide 42 by 42.

$$x=1$$

Now solve the equation x=\frac{0±42}{42} when ± is minus. Divide -42 by 42.

$$x=-1$$

The equation is now solved.

$$x=1 x=-1$$