A number is such that if you square it and then subtract twice the number, the result is 80. What is the number?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 10.
Let the number = x
x2 – 2x = 80
⇒ x2 – 2x – 80 = 0
⇒ x2 – 10x + 8x – 80 = 0
⇒ (x – 10)(x + 8) = 0
⇒ x = 10 or –8