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MediumQuadratic EquationsAlgebra

Solve 2x2+3x−2=02x^2 + 3x - 2 = 0.

Leading coefficient other than one: the quadratic formula works every time.

Try it first: work the problem on paper, then open the solution below and compare each step.
Show the step-by-step solution

Final answer

x1=−2,x2=12x_1 = -2,\quad x_2 = \frac{1}{2}

How we read your problem

A quadratic equation in x: solve with the quadratic formula.

2 x2+3 x−2=02~{ x}^{2}+3~ x-2 = 0

Step-by-step solution

  1. Start with the equation

    2 x2+3 x−2=02~{ x}^{2}+3~ x-2 = 0
  2. Move every term to one side to get standard form

    2x2+3x−2=02x^{2} + 3x - 2 = 0
  3. Compute the discriminant

    Δ=b2−4ac=32−4⋅2⋅(−2)=25\Delta = b^2 - 4ac = 3^2 - 4 \cdot 2 \cdot (-2) = 25
  4. Δ > 0, so there are two distinct real roots

  5. Apply the quadratic formula

    x=−b±Δ2a=−3±254=−3±54x = \frac{-b \pm \sqrt{\Delta}}{2a} = \frac{-3 \pm \sqrt{25}}{4} = \frac{-3 \pm 5}{4}
  6. Simplify each root

    x1=−3−54=−2,x2=−3+54=12x_1 = \frac{-3 - 5}{4} = -2,\quad x_2 = \frac{-3 + 5}{4} = \frac{1}{2}
  7. Factored form

    2x2+3x−2=(x+2)(2x−1)2x^2 + 3x - 2 = (x + 2)(2x - 1)

Formulas used

  • Quadratic formula

    x=−b±b2−4ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
  • Discriminant

    Δ=b2−4ac\Delta = b^2 - 4ac
  • Vertex

    (−b2a, c−b24a)\left(-\frac{b}{2a},\ c - \frac{b^2}{4a}\right)

The quadratic formula gives every solution of ax² + bx + c = 0.

Verification

  • x = -2: left side = 0, right side = 0 ✓
  • x = 0.5: left side = 0, right side = 0 ✓

About quadratic equations

Solve by factoring, completing the square or the quadratic formula; use the discriminant.

Quadratic formula

The roots of a quadratic in standard form.

x=−b±b2−4ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
Discriminant

Its sign tells whether there are two real, one repeated, or two complex roots.

Δ=b2−4ac\Delta = b^2 - 4ac

Check your own work