Question

Q.8. For what value(s) of k, the Q.E.
kx2 -42x + 9 = 0 is a perfect square?
*
1)49
2)94
3)36
4)81​

Answer 1

Answer:

1) 49 is the answer

Step-by-step explanation:

$k {x}^{2} - 42x + 9 = 0 \\ \\ ( \sqrt{k} x) {}^{2} - 2 \times \sqrt{k} \times 3 + ( {3)}^{2} = 0 \\ \\ 42 = 6 \times \sqrt{k} \\ \sqrt{k} = 7 \\ \\ k = {7}^{2} = 49$