Question 12 Marks
Answer the following and justify:
Can the quadratic polynomial $x^2 + kx + k$ have equal zeroes for some odd integer $k > 1?$
Can the quadratic polynomial $x^2 + kx + k$ have equal zeroes for some odd integer $k > 1?$
Answer
View full question & answer→Let $p(x) = x^2 + kx + k$
For equal zeroes,$ b^2 - 4ac = 0$
$\Rightarrow (k)^2 - 4(1) (k) = 0$
$\Rightarrow k^2 - 4k = 0$
$\Rightarrow k(k - 4) = 0$
$\Rightarrow k = 0 or k = 4$
But $k > 1$ so $k = 4$
The given quadratic polynomial has equal zeroes at $k = 4.$
For equal zeroes,$ b^2 - 4ac = 0$
$\Rightarrow (k)^2 - 4(1) (k) = 0$
$\Rightarrow k^2 - 4k = 0$
$\Rightarrow k(k - 4) = 0$
$\Rightarrow k = 0 or k = 4$
But $k > 1$ so $k = 4$
The given quadratic polynomial has equal zeroes at $k = 4.$