Find the Roots (Zeros) f(x)=-x^4+x^3+2x^2

$f (x) = - x^{4} + x^{3} + 2 x^{2}$

Step 1

Set $- x^{4} + x^{3} + 2 x^{2}$ equal to $0$ .

$- x^{4} + x^{3} + 2 x^{2} = 0$

Step 2

Solve for $x$ .

Factor the left side of the equation.

Factor $- x^{2}$ out of $- x^{4} + x^{3} + 2 x^{2}$ .

Factor $- x^{2}$ out of $- x^{4}$ .

$- x^{2} x^{2} + x^{3} + 2 x^{2} = 0$

Factor $- x^{2}$ out of $x^{3}$ .

$- x^{2} x^{2} - x^{2} (- x) + 2 x^{2} = 0$

Factor $- x^{2}$ out of $2 x^{2}$ .

$- x^{2} x^{2} - x^{2} (- x) - x^{2} \cdot - 2 = 0$

Factor $- x^{2}$ out of $- x^{2} (x^{2}) - x^{2} (- x)$ .

$- x^{2} (x^{2} - x) - x^{2} \cdot - 2 = 0$

Factor $- x^{2}$ out of $- x^{2} (x^{2} - x) - x^{2} (- 2)$ .

$- x^{2} (x^{2} - x - 2) = 0$

Factor.

Factor $x^{2} - x - 2$ 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 $- 2$ and whose sum is $- 1$ .

$- 2, 1$

Write the factored form using these integers.

$- x^{2} ((x - 2) (x + 1)) = 0$

Remove unnecessary parentheses.

$- x^{2} (x - 2) (x + 1) = 0$

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

$x^{2} = 0$

$x - 2 = 0$

$x + 1 = 0$

Set $x^{2}$ equal to $0$ and solve for $x$ .

Set $x^{2}$ equal to $0$ .

$x^{2} = 0$

Solve $x^{2} = 0$ for $x$ .

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

$x = \pm \sqrt{0}$

Simplify $\pm \sqrt{0}$ .

Rewrite $0$ as $0^{2}$ .

$x = \pm \sqrt{0^{2}}$

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

$x = \pm 0$

Plus or minus $0$ is $0$ .

$x = 0$

Set $x - 2$ equal to $0$ and solve for $x$ .

Set $x - 2$ equal to $0$ .

$x - 2 = 0$

Add $2$ to both sides of the equation.

$x = 2$

Set $x + 1$ equal to $0$ and solve for $x$ .

Set $x + 1$ equal to $0$ .

$x + 1 = 0$

Subtract $1$ from both sides of the equation.

$x = - 1$

The final solution is all the values that make $- x^{2} (x - 2) (x + 1) = 0$ true.

$x = 0, 2, - 1$

Step 3

Find the Roots (Zeros) f(x)=-x^4+x^3+2x^2

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