For what value of y is the expression \(\frac{y + 2}{y^{2} - 3y - 10}\) undefined?

  • A y = 0
  • B y = 2
  • C y = 3
  • D y = 5
  • E y = 10
waec 1991mathematics

The correct answer is D. y = 5

\(\frac{y + 2}{y^2 - 3y - 10}\) 

\(y^2 - 3y - 10 = 0 \implies y^2 - 5y + 2y - 10 = 0\)

\(y(y - 5) + 2(y - 5) = 0\)

\((y - 5)(y + 2) = 0\)

\(\frac{y + 2}{(y - 5)(y + 2)} = \frac{1}{y - 5}\)

\(\therefore\) At y = 5, the expression \(\frac{y + 2}{y^2 - 3y - 10}\) is undefined.

Previous question Next question