JAMB - Mathematics (2025 - No. 11)
Y is partly constant and partly varies as x. When x = 3, y = 7 and when x = 5, y = 11. Find the constants of variation.
2,3
1,2
3,2
3,4
Explanation
Form: y = a + b x.
7 = a + 3b. - - - - - - - 1
11 = a + 5b. - - - - - - 2
Solve both equations using the elimination method
Subtract: 4 = 2b ⇒ b = 2.
put b = 2 into eqn 1
a + 6 = 7 ⇒ a = 1. Constants a = 1 (constant part), b = 2 (variation constant).
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