Solve 2x^2-x-15=0

Question

Solve the quadratic equation

Solve by factoring

Solve using the quadratic formula

Solve by completing the square

x_{1} = - \frac{5}{2}, x_{2} = 3

Alternative Form

x_{1} = - 2.5, x_{2} = 3

Evaluate

2 x^{2} - x - 15 = 0

Factor the expression

More Steps

Evaluate

2 x^{2} - x - 15

Rewrite the expression

2 x^{2} + (5 - 6) x - 15

Calculate

2 x^{2} + 5 x - 6 x - 15

Rewrite the expression

x \times 2 x + x \times 5 - 3 \times 2 x - 3 \times 5

Factor out x from the expression

x (2 x + 5) - 3 \times 2 x - 3 \times 5

Factor out - 3 from the expression

x (2 x + 5) - 3 (2 x + 5)

Factor out 2 x + 5 from the expression

(x - 3) (2 x + 5)

(x - 3) (2 x + 5) = 0

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

x - 3 = 0 2 x + 5 = 0

Solve the equation for x

More Steps

Evaluate

x - 3 = 0

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

x = 0 + 3

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

x = 3

x = 3 2 x + 5 = 0

Solve the equation for x

More Steps

Evaluate

2 x + 5 = 0

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

2 x = 0 - 5

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

2 x = - 5

Divide both sides

\frac{2 x}{2} = \frac{- 5}{2}

Divide the numbers

x = \frac{- 5}{2}

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

x = - \frac{5}{2}

x = 3 x = - \frac{5}{2}

Solution

x_{1} = - \frac{5}{2}, x_{2} = 3

Alternative Form

x_{1} = - 2.5, x_{2} = 3

Show Solution