Solve 4x² - 16x + 15 = 0.

Correct Answer is : x = 1 12\;1/221 or x = 2 12\;1/221

Correct Answer is : x = 1 12\;1/221 or x = 2 12\;1/221

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WAEC Mathematics 2019 Paper

Question : 13

Total: 50

Solve

4x^{2}

- 16x + 15 = 0.

Solution:

Concept:

Factorising the quadratic by splitting the middle term helps find the values of

x

Explanation:

Start with

4x^{2} - 16x + 15 = 0

Find two numbers whose product is

4 \times 15 = 60

and whose sum is

-16

The required numbers are

-6

and

-10

Rewrite the equation:

4x^{2} - 6x - 10x + 15 = 0

Group and factor:

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

Factor out the common binomial:

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

Set each factor equal to zero.

2x - 3 = 0 \Rightarrow x = \frac{3}{2} = 1\frac{1}{2}

2x - 5 = 0 \Rightarrow x = \frac{5}{2} = 2\frac{1}{2}

Answer:

x = 1\frac{1}{2}

x = 2\frac{1}{2}

Therefore, the correct option is B.

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