WAEC - Mathematics (2022 - No. 13)
If 5x + 3y=4 and 5x-3y= 2, what is the value of (25x\(^2\) -9y\(^2\))?
20
16
2
8
Forklaring
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