Solve the equation 3x² - 4x - 5 = 0

Correct Answer is : x = 2.12 or − 0.79

Correct Answer is : x = 2.12 or − 0.79

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JAMB Mathematics 2015 Paper

Question : 11

Total: 61

3x^2 - 4x - 5 = 0

Solution:

Concept:

Use the quadratic formula to solve a quadratic equation of the form

ax^2 + bx + c = 0

Explanation:

From

3x^2 - 4x - 5 = 0

, we have

a = 3

b = -4

, and

c = -5

The quadratic formula is:

x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substitute the values:

x = \frac{-(-4) \pm \sqrt{(-4)^2 - 4(3)(-5)}}{2(3)}

Simplify the numerator and denominator:

x = \frac{4 \pm \sqrt{16 + 60}}{6}

x = \frac{4 \pm \sqrt{76}}{6}

Since

\sqrt{76} \approx 8.72

, we get:

x = \frac{4 \pm 8.72}{6}

Calculate each root:

x = \frac{4 + 8.72}{6} \approx 2.12

x = \frac{4 - 8.72}{6} \approx -0.79

Answer:

x = 2.12

x = -0.79

(Option B).

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