Find the Roots (Zeros) F(x)=x^3-6x^2+7x-2

$F (x) = x^{3} - 6 x^{2} + 7 x - 2$

Step 1

Set $x^{3} - 6 x^{2} + 7 x - 2$ equal to $0$ .

$x^{3} - 6 x^{2} + 7 x - 2 = 0$

Step 2

Solve for $x$ .

Factor $x^{3} - 6 x^{2} + 7 x - 2$ using the rational roots test.

If a polynomial function has integer coefficients, then every rational zero will have the form $\frac{p}{q}$ where $p$ is a factor of the constant and $q$ is a factor of the leading coefficient.

$p = \pm 1, \pm 2 q = \pm 1$

Find every combination of $\pm \frac{p}{q}$ . These are the possible roots of the polynomial function.

$\pm 1, \pm 2$

Substitute $1$ and simplify the expression. In this case, the expression is equal to $0$ so $1$ is a root of the polynomial.

Substitute $1$ into the polynomial.

$1^{3} - 6 \cdot 1^{2} + 7 \cdot 1 - 2$

Raise $1$ to the power of $3$ .

$1 - 6 \cdot 1^{2} + 7 \cdot 1 - 2$

Raise $1$ to the power of $2$ .

$1 - 6 \cdot 1 + 7 \cdot 1 - 2$

Multiply $- 6$ by $1$ .

$1 - 6 + 7 \cdot 1 - 2$

Subtract $6$ from $1$ .

$- 5 + 7 \cdot 1 - 2$

Multiply $7$ by $1$ .

$- 5 + 7 - 2$

Add $- 5$ and $7$ .

$2 - 2$

Subtract $2$ from $2$ .

$0$

Since $1$ is a known root, divide the polynomial by $x - 1$ to find the quotient polynomial. This polynomial can then be used to find the remaining roots.

$\frac{x^{3} - 6 x^{2} + 7 x - 2}{x - 1}$

Divide $x^{3} - 6 x^{2} + 7 x - 2$ by $x - 1$ .

Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of $0$ .

$x$

$1$

$x^{3}$

$6 x^{2}$

$7 x$

$2$

Divide the highest order term in the dividend $x^{3}$ by the highest order term in divisor $x$ .

					$x^{2}$
	$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$

Multiply the new quotient term by the divisor.

				$x^{2}$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			+	$x^{3}$	-	$x^{2}$

The expression needs to be subtracted from the dividend, so change all the signs in $x^{3} - x^{2}$

				$x^{2}$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$

Pull the next terms from the original dividend down into the current dividend.

				$x^{2}$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$

Divide the highest order term in the dividend $- 5 x^{2}$ by the highest order term in divisor $x$ .

				$x^{2}$	-	$5 x$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$

Multiply the new quotient term by the divisor.

				$x^{2}$	-	$5 x$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					-	$5 x^{2}$	+	$5 x$

The expression needs to be subtracted from the dividend, so change all the signs in $- 5 x^{2} + 5 x$

				$x^{2}$	-	$5 x$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$	-	$5 x$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$

Pull the next terms from the original dividend down into the current dividend.

				$x^{2}$	-	$5 x$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$	-	$2$

Divide the highest order term in the dividend $2 x$ by the highest order term in divisor $x$ .

				$x^{2}$	-	$5 x$	+	$2$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$	-	$2$

Multiply the new quotient term by the divisor.

				$x^{2}$	-	$5 x$	+	$2$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$	-	$2$
							+	$2 x$	-	$2$

The expression needs to be subtracted from the dividend, so change all the signs in $2 x - 2$

				$x^{2}$	-	$5 x$	+	$2$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$	-	$2$
							-	$2 x$	+	$2$

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$	-	$5 x$	+	$2$
$x$	-	$1$		$x^{3}$	-	$6 x^{2}$	+	$7 x$	-	$2$
			-	$x^{3}$	+	$x^{2}$
					-	$5 x^{2}$	+	$7 x$
					+	$5 x^{2}$	-	$5 x$
							+	$2 x$	-	$2$
							-	$2 x$	+	$2$
										$0$

Since the remander is $0$ , the final answer is the quotient.

$x^{2} - 5 x + 2$

Write $x^{3} - 6 x^{2} + 7 x - 2$ as a set of factors.

$(x - 1) (x^{2} - 5 x + 2) = 0$

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

$x - 1 = 0$

$x^{2} - 5 x + 2 = 0$

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

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

$x - 1 = 0$

Add $1$ to both sides of the equation.

$x = 1$

Set $x^{2} - 5 x + 2$ equal to $0$ and solve for $x$ .

Set $x^{2} - 5 x + 2$ equal to $0$ .

$x^{2} - 5 x + 2 = 0$

Solve $x^{2} - 5 x + 2 = 0$ for $x$ .

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Substitute the values $a = 1$ , $b = - 5$ , and $c = 2$ into the quadratic formula and solve for $x$ .

$\frac{5 \pm \sqrt{{(- 5)}^{2} - 4 \cdot (1 \cdot 2)}}{2 \cdot 1}$

Simplify.

Simplify the numerator.

Raise $- 5$ to the power of $2$ .

$x = \frac{5 \pm \sqrt{25 - 4 \cdot 1 \cdot 2}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 2$ .

Multiply $- 4$ by $1$ .

$x = \frac{5 \pm \sqrt{25 - 4 \cdot 2}}{2 \cdot 1}$

Multiply $- 4$ by $2$ .

$x = \frac{5 \pm \sqrt{25 - 8}}{2 \cdot 1}$

Subtract $8$ from $25$ .

$x = \frac{5 \pm \sqrt{17}}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{5 \pm \sqrt{17}}{2}$

The final answer is the combination of both solutions.

$x = \frac{5 + \sqrt{17}}{2}, \frac{5 - \sqrt{17}}{2}$

The final solution is all the values that make $(x - 1) (x^{2} - 5 x + 2) = 0$ true.

$x = 1, \frac{5 + \sqrt{17}}{2}, \frac{5 - \sqrt{17}}{2}$

Step 3

The result can be shown in multiple forms.

Exact Form:

$x = 1, \frac{5 + \sqrt{17}}{2}, \frac{5 - \sqrt{17}}{2}$

Decimal Form:

$x = 1, 4.56155281 \dots, 0.43844718 \dots$

Step 4

Find the Roots (Zeros) F(x)=x^3-6x^2+7x-2

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