Skip to content
dronacharya.ai
← JEE Main 2016 · 9 Apr · Shift 1
MathematicsSingle correct+4 / -1Question 63 of 90

JEE Main 2016 · 9 Apr · Shift 1, Mathematics question 63

If the equations x2+bx−1=0x^2+bx-1=0 and x2+x+b=0x^2+x+b=0 have a common root different from −1, then |b| is equal to :

Choose one option
Answer and worked solution

Official answer: D

Subtracting, a common root α satisfies (b−1)α=b+1(b-1)\alpha=b+1. Substituting into α2+α+b=0\alpha^2+\alpha+b=0 leads to b(b2+3)=0b(b^2+3)=0. b = 0 gives α = −1, which is excluded, so b2=−3b^2=-3 and ∣b∣=3|b|=\sqrt3 (b is then not real).

Topics:Roots and coefficients
← Previous questionNext question →