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Question

Find the value of p for p(x)=(p+1)x2-6(p+1)x+3(p+q)=0,has equal roots. Also find the roots

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Solution

The given equation is a quadratic equation.
The root of a quadratic equation is given by the equation fraction numerator negative b plus-or-minus square root of b squared minus 4 a c end root over denominator 2 a end fraction
Also we know that if the roots are equal then b squared minus 4 a c =0
(if it is greater than 0,there will be 2 distinct roots,if less than zero then the roots are imaginary)

​​​​​​Let r be the root of the equation, and since the roots are equal
r space equals fraction numerator negative b plus-or-minus 0 over denominator 2 a end fraction equals fraction numerator negative b over denominator 2 a end fraction
Here b = -6(p+1)
a = p+1
So
r space equals space fraction numerator 6 left parenthesis p plus 1 right parenthesis over denominator 2 left parenthesis p plus 1 right parenthesis end fraction equals 3
So the root of the equation is 3.
A root of an equation means the possible values of x in the equation. So we can substitute x=3 in the equation.Then,
9 left parenthesis p plus 1 right parenthesis minus 18 left parenthesis p plus 1 right parenthesis plus 3 left parenthesis p plus q right parenthesis equals 0
On solving we get,

P equals fraction numerator q minus 3 over denominator 2 end fraction

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