Solve 3x^2 - 8x - 80 = 0

Question

Solve the quadratic equation

Solve by factoring

Solve using the quadratic formula

Solve by completing the square

x_{1} = - 4, x_{2} = \frac{20}{3}

Alternative Form

x_{1} = - 4, x_{2} = 6. \dot{6}

Evaluate

3 x^{2} - 8 x - 80 = 0

Factor the expression

More Steps

Evaluate

3 x^{2} - 8 x - 80

Rewrite the expression

3 x^{2} + (- 20 + 12) x - 80

Calculate

3 x^{2} - 20 x + 12 x - 80

Rewrite the expression

x \times 3 x - x \times 20 + 4 \times 3 x - 4 \times 20

Factor out x from the expression

x (3 x - 20) + 4 \times 3 x - 4 \times 20

Factor out 4 from the expression

x (3 x - 20) + 4 (3 x - 20)

Factor out 3 x - 20 from the expression

(x + 4) (3 x - 20)

(x + 4) (3 x - 20) = 0

When the product of factors equals 0,at least one factor is 0

3 x - 20 = 0 x + 4 = 0

Solve the equation for x

More Steps

Evaluate

3 x - 20 = 0

Move the constant to the right-hand side and change its sign

3 x = 0 + 20

Removing 0 doesn't change the value,so remove it from the expression

3 x = 20

Divide both sides

\frac{3 x}{3} = \frac{20}{3}

Divide the numbers

x = \frac{20}{3}

x = \frac{20}{3} x + 4 = 0

Solve the equation for x

More Steps

Evaluate

x + 4 = 0

Move the constant to the right-hand side and change its sign

x = 0 - 4

Removing 0 doesn't change the value,so remove it from the expression

x = - 4

x = \frac{20}{3} x = - 4

Solution

x_{1} = - 4, x_{2} = \frac{20}{3}

Alternative Form

x_{1} = - 4, x_{2} = 6. \dot{6}

Show Solution