Question

Five times a certain whole number is equal to three less than twice the square of the number. Find the number.

Answer 1

Let number = x
Now according to the condition,
5x = 2x² - 3
⇒ 2x² - 5x - 3 = 0
⇒ 2x² - 6x + x - 3 = 0
⇒ 2x(x - 3) + 1 (x - 3) = 0
⇒ (x - 3)(2x + 1) = 0
Either x - 3 = 0,
then x = 3
or
2x + 1 = 0,
then 2x = -1

⇒ x `-(1)/(2)`

But it is not possible as the number is whole number.
∴ Number = 3.