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WAEC Mathematics 2020 Paper

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Question : 44

Total: 48

The graph of the equations y = 2x + 5 and y = 2x

^2

+ x - 1 are shown. Use the information above to answer this question.

Find the point of intersection of the two graphs.

(2.0, 9.0) and (-1.5, 2.0)
(2.0, 8.5) and (-1.5, 2.0)
(2.0, 8.0) and (-1.5, 2.5)
(2.0, 7.5) and (-1.5, 2.5)

Solution:

Concept:

The points where the two graphs meet must satisfy both equations simultaneously.

Explanation:

Equate the two equations:

2x+5 = 2x^2+x-1

.

Rearrange:

0 = 2x^2 - x - 6

.

Factorise:

2x^2 - x - 6 = (2x+3)(x-2) = 0

.

So,

x = 2

or

x = -\frac{3}{2} = -1.5

.

Substitute into

y = 2x+5

.

When

x = 2

,

y = 2(2)+5 = 9

.

When

x = -1.5

,

y = 2(-1.5)+5 = 2

.

The intersection points are

(2.0,9.0)

and

(-1.5,2.0)

.

Answer:

Option A:

(2.0,9.0)

and

(-1.5,2.0)

.

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