bhatiamanu05 wrote:

adg142000 wrote:

There are 2 equations \(x^2+ax+c\) and \(x^2+bx +a\) which have a common root. What is the value of (a+b)?

Note: I am not too sure of whether the question was value of a+b or max value of a+b but the question was either of these 2.I dont have the answer options as well.This appeared in one of the aptitude papers and I got entangled in this question so wanted to know how to approach this

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The approach to this type of questions depends upon basically two parts.

Sum of roots of the equation and product of the roots of a quadratic equation.

ax^2+bx+c=0 this equation has two roots R and Y.

Sum of roots is given (R+Y) = -b/a

Product of roots is given (R.Y)= c/a

You can write both the equation in this format and try to find a relation between a and b.

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Thanks,

AB

I know this formula , so accordingly for the 1st eqn if a1 and a2 are roots and b1 &b2 for 2nd eqn so :

a1+a2=-a, b1+b2=-b

a1a2=c, b1b2=a

now a+b=-(a1+a2+b1+b2)

now if one of the common root is x=a2=b2

a+b=-(a1+x+b1+x)=-(c/x+a/x+2x),,

I am not sure how to proceed after this ,, is there a way we can find out what x is and values of c and a as well?? i remember all the options were numerical values. two of which i remember was -1 and 1

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