JAMB - Mathematics (1984 - No. 16)

A straight line y = mx meets the curve y = x2 - 12x + 40 in two distinct points. If one of them is (5, 5) find the other
(5, 6)
(8, 8)
(8, 5)
(7,7)
(7, 5)

Explanation

When y = 5, y = x2 - 12x + 40, becomes

x2 - 12x + 40 = 5

x2 - 12x + 40 - 5 = 0

x2 + 12x + 35 = 0

x2 - 7x - 5x + 35 = 0

x(x - 7) - 5(x - 7) = 0

= (x - 5)(x - 7)

x = 5 or 7

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