Solve (x+3)(x-3)=40

$$( x + 3 ) ( x - 3 ) = 40$$

Solve for x

$$x=-7$$

$$x=7$$

Steps by Finding Square Root

Consider \left(x+3\right)\left(x-3\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 3.

$$x^{2}-9=40$$

Add 9 to both sides.

$$x^{2}=40+9$$

Add 40 and 9 to get 49.

$$x^{2}=49$$

Take the square root of both sides of the equation.

$$x=7 x=-7$$

Steps Using the Quadratic Formula

Consider \left(x+3\right)\left(x-3\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 3.

$$x^{2}-9=40$$

Subtract 40 from both sides.

$$x^{2}-9-40=0$$

Subtract 40 from -9 to get -49.

$$x^{2}-49=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 0 for b, and -49 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\left(-49\right)}}{2}$$

Square 0.

$$x=\frac{0±\sqrt{-4\left(-49\right)}}{2}$$

Multiply -4 times -49.

$$x=\frac{0±\sqrt{196}}{2}$$

Take the square root of 196.

$$x=\frac{0±14}{2}$$

Now solve the equation x=\frac{0±14}{2} when ± is plus. Divide 14 by 2.

$$x=7$$

Now solve the equation x=\frac{0±14}{2} when ± is minus. Divide -14 by 2.

$$x=-7$$

The equation is now solved.

$$x=7 x=-7$$