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JAMB Mathematics 2018 Paper

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Question : 36

Total: 62

Evaluate (2√3 - 4) (2√3 + 4)

-4
-2
2
4

Solution:

Concept:

The product is of the form

(a - b)(a + b)

, which equals

a^2 - b^2

.

Explanation:

Let

a = 2\sqrt{3}

and

b = 4

.

Then

(2\sqrt{3} - 4)(2\sqrt{3} + 4) = (2\sqrt{3})^2 - 4^2

.

Now

(2\sqrt{3})^2 = 4 \times 3 = 12

.

And

4^2 = 16

.

So the result is

12 - 16 = -4

.

The two brackets are conjugates, so the middle terms cancel out.

Answer:

-4

Option A.

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