Solve 2x^2-x-1=0 - ScanMath

Question

Solve the quadratic equation

Solve by factoring

Solve using the quadratic formula

Solve by completing the square

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

Alternative Form

x_{1} = - 0.5, x_{2} = 1

Evaluate

2 x^{2} - x - 1 = 0

Factor the expression

More Steps

Evaluate

2 x^{2} - x - 1

Rewrite the expression

2 x^{2} + (1 - 2) x - 1

Calculate

2 x^{2} + x - 2 x - 1

Rewrite the expression

x \times 2 x + x - 2 x - 1

Factor out x from the expression

x (2 x + 1) - 2 x - 1

Factor out - 1 from the expression

x (2 x + 1) - (2 x + 1)

Factor out 2 x + 1 from the expression

(x - 1) (2 x + 1)

(x - 1) (2 x + 1) = 0

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

x - 1 = 0 2 x + 1 = 0

Solve the equation for x

More Steps

Evaluate

x - 1 = 0

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

x = 0 + 1

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

x = 1

x = 1 2 x + 1 = 0

Solve the equation for x

More Steps

Evaluate

2 x + 1 = 0

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

2 x = 0 - 1

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

2 x = - 1

Divide both sides

\frac{2 x}{2} = \frac{- 1}{2}

Divide the numbers

x = \frac{- 1}{2}

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

x = - \frac{1}{2}

x = 1 x = - \frac{1}{2}

Solution

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

Alternative Form

x_{1} = - 0.5, x_{2} = 1

Show Solution