Y is partly constant and partly varies as x. When x = 3, y =...

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.

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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