y is directly proportional to (x-1)^2. When x=5, y=4. Find y when x=7.
The trick to finding y in this question is to interpret the clue in the question of 'directly proportional'. Directly proportional means that the y and the (x-1)2 scale by the same amount. Another way of saying this is that y is equal to (x-1)2 multiplied by some constant, say C, giving us: y = C*(x-1)2From here we can calculate C by inputting the information provided: y=4 when x=5.4 = C*(5-1)2 = C42 = C16Therefore C = 0.25Finally, we substitute x=7 to find the final answer:y = 0.25*(7-1)2 = 0.2562 = 0.2536 = 9
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