The minimum possible value of the sum of the squares of the roots of the equation x^2 + (a + 3)x – (a + 5) = 0 is
A) 1
B) 2
C) 3
D) 4
Answer
Option (C)
Solution
From CAT 2017 – Quantitative Aptitude – Algebra – Quadratic Equations, we can see that,
b and c can be the roots of the given equation.
We have to find, b^2 + c^2 = (b+c)^2 – 2bc
b+c = -(a+3) and bc = -(a+5)
b^2 + c^2 = (a+3)^2 + 2(a+5) = a^2 + 8a + 19
Min value of a quadratic equation = -Discriminant (D)/4*First term
D = b^2 – 4ac = 64 – 76 = -12
Min value = 12/4 = 3
Option (C)
a) 1000+ Videos covering entire CAT syllabus b) 2 Live Classes (online) every week for doubt clarification c) Study Material & PDFs for practice and understanding d) 10 Mock Tests in the latest pattern e) Previous Year Questions solved on video