JAMB 1992 · UME · Q12

Quadratics & their graphs

Solve the equation $y - 11\sqrt y + 24 = 0$ .

Worked solution (try it first)

Let $u = \sqrt y$ , so $y = u^2$ and the equation is $u^2 - 11u + 24 = 0$ .
Factorise: $(u - 3)(u - 8) = 0$ , so $\sqrt y = 3$ or $\sqrt y = 8$ .
Square: $y = 9$ or $y = 64$ , option B.

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