JAMB 1984 · UME · Q41

Quadratics & their graphs

The larger value of $y$ for which $(y - 1)^2 = 4y - 7$ is

Worked solution (try it first)

Expand the left side: $y^2 - 2y + 1 = 4y - 7$ .
Bring everything to one side: $y^2 - 6y + 8 = 0$ .
Factorise: $(y - 2)(y - 4) = 0$ , so $y = 2$ or $y = 4$ .
The larger value is 4, option B.

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