CAT 2016 Quantitative Ability

Question : 3 of 34

Marks: +1, -0

If ‘a’ and ‘b’ are the roots of the equation

x^2 + 7x + 4 = 0,

where a > b, then find the value of

({2}/{7a})+(\;\;{1}/{3.5b})+ab

Solution:

As ‘a’ and ‘b’ are the roots of the given equation,
a + b = -7
ab = 4
The given expression can be rewritten as

\;\;{2}/{7}(\;\;{a+b}/{ab})+ab=\;\;{2}/{7}(\;\;{-7}/{4})+4=\;\;{7}/{2}

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