Questions :
Twenty one times of a positive number is less than its square by 100. The value of the positive number is:
Options :
- 25
- 26
- 42
- 41
correct answer : a)
Suppose, the positive number be x.
According to the question,
x² – 21x + 100 = 0
⇒ x² – 25x + 4x – 100 = 0
⇒ x(x – 25) + 4(x – 25) = 0
⇒ (x – 25)(x + 4) = 0
∴ x = 25 because x ≠ –4