WAEC - Mathematics (2020 - No. 21)
A man is five times as old as his son. In four years' time, the product of their ages would be 340. If the son's age is y, express the product of their ages in terms of y.
5y\(^2 - 16y - 380 = 0\)
5y\(^2 - 24y - 380 = 0\)
5y\(^2 - 16y - 330 = 0\)
5y\(^2 + 24y - 324 = 0\)
Spiegazione
Man = x, Son = y
x = 5y
(x + 4)(y + 4) = 350
(5y + 4)(y + 4) = 340
5y\(^2\) + 20y + 4y + 16 - 240 = 0
5y\(^2\) + 24y - 324 = 0