Solve Using the Quadratic Formula x^4-40x^2+144=0

$x^{4} - 40 x^{2} + 144 = 0$

Substitute $u = x^{2}$ into the equation. This will make the quadratic formula easy to use.

$u^{2} - 40 u + 144 = 0$

$u = x^{2}$

Factor $u^{2} - 40 u + 144$ using the AC method.

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $144$ and whose sum is $- 40$ .

$- 36, - 4$

Write the factored form using these integers.

$(u - 36) (u - 4) = 0$

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$u - 36 = 0$

$u - 4 = 0$

Set $u - 36$ equal to $0$ and solve for $u$ .

Set $u - 36$ equal to $0$ .

$u - 36 = 0$

Add $36$ to both sides of the equation.

$u = 36$

Set $u - 4$ equal to $0$ and solve for $u$ .

Set $u - 4$ equal to $0$ .

$u - 4 = 0$

Add $4$ to both sides of the equation.

$u = 4$

The final solution is all the values that make $(u - 36) (u - 4) = 0$ true.

$u = 36, 4$

Substitute the real value of $u = x^{2}$ back into the solved equation.

$x^{2} = 36$

${(x^{2})}^{1} = 4$

Solve the first equation for $x$ .

$x^{2} = 36$

Solve the equation for $x$ .

Take the square root of both sides of the equation to eliminate the exponent on the left side.

$x = \pm \sqrt{36}$

Simplify $\pm \sqrt{36}$ .

Rewrite $36$ as $6^{2}$ .

$x = \pm \sqrt{6^{2}}$

Pull terms out from under the radical, assuming positive real numbers.

$x = \pm 6$

The complete solution is the result of both the positive and negative portions of the solution.

First, use the positive value of the $\pm$ to find the first solution.

$x = 6$

Next, use the negative value of the $\pm$ to find the second solution.

$x = - 6$

The complete solution is the result of both the positive and negative portions of the solution.

$x = 6, - 6$

Solve the second equation for $x$ .

${(x^{2})}^{1} = 4$

Solve the equation for $x$ .

Remove parentheses.

$x^{2} = 4$

Take the square root of both sides of the equation to eliminate the exponent on the left side.

$x = \pm \sqrt{4}$

Simplify $\pm \sqrt{4}$ .

Rewrite $4$ as $2^{2}$ .

$x = \pm \sqrt{2^{2}}$

Pull terms out from under the radical, assuming positive real numbers.

$x = \pm 2$

The complete solution is the result of both the positive and negative portions of the solution.

First, use the positive value of the $\pm$ to find the first solution.

$x = 2$

Next, use the negative value of the $\pm$ to find the second solution.

$x = - 2$

The complete solution is the result of both the positive and negative portions of the solution.

$x = 2, - 2$

The solution to $x^{4} - 40 x^{2} + 144 = 0$ is $x = 6, - 6, 2, - 2$ .

$x = 6, - 6, 2, - 2$

Solve Using the Quadratic Formula x^4-40x^2+144=0

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