Quantitative Aptitude – Algebra – Quadratic Equation – If x + 1 = x^2


Quantitative Aptitude – Algebra – Quadratic Equation


Question


CAT 2017 - Forenoon slot - Quantitative Aptitude - Algebra - Quadratic Equation - If x + 1 = x^2
If x + 1 = x^2 and x > 0, then 2x^4 is

A) 6 + 4√5
B) 3 + 5√5
C) 5 + 3√5
D) 7 + 3√5

Answer


Option (D)

Solution


As per CAT 2017 – Quantitative Aptitude – Algebra – Quadratic Equation, we can see that
x+1=x^2
Find out the roots of x = [1+/- root(5)]/2
X2 = [3 +/- √5]/2
X4 = [7 +/-3√5]/2
2×4 = 7 +/- 3√5
As the only option is 7 + 3√5 So, we go with that.
Option (D)

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