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

Alternative Form

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

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

x - 4 = 0 3 x + 20 = 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 = 4 3 x + 20 = 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}

Use \frac{- a}{b} = \frac{a}{- b} = - \frac{a}{b} to rewrite the fraction

x = - \frac{20}{3}

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

Solution

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

Alternative Form

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

Show Solution