If x2 - 5x + 1 = 0
Find (x2 - 11) (x2 - 12)
Answer & explanation
Correct answer: option 2
Given, x2 - 5x + 1 = 0
x2 = 5x - 1 ---------------(1)
put the value of x2 in below equation
= (x2 - 11) (x2 - 12)
= (5x - 1 - 11) ( 5x - 1 - 12)
= (5x - 12) (5x - 13) = 25x2 - 125x + 156
25(x2 - 5x) + 156 ⇒ x2 - 5x = -1 from equation (1)
-25 + 156 = 131