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WAEC Mathematics 2022 Paper

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Question : 13

Total: 47

If 5x + 3y=4 and 5x-3y= 2, what is the value of (25x

^2

^2

)?

20
16
2
8

Solution:

5x + 3y=4

5x-3y= 2

Using elimination method

5x + 3y=4 → 5x + 3y=4

-[5x-3y= 2] → -5x +3y= -2

6y = 2

y → 1/3 and x = 3/5

solving (25x $^2$ -9y $^2$ )

25 * [3/5] $^2$ -9 * [1/3] $^2$

25 * $\;\frac{9}{25}$ - 9 $\;\frac{1}{9}$

9 - 1 = 8

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