1.

If x = 1 is a common root of the equations ax2 + ax + 3 = 0 and x2 + x + b = 0, then the value of ab is : A) 3B) 6 C) 3.5 D) -3

Answer»

Correct option is (A) 3

Given that x = 1 is a root of equation \(ax^2+ax+3=0\)

\(\therefore a.1^2+a.1+3=0\)

\(\Rightarrow\) a+a+3 = 0

\(\Rightarrow\) 2a = -3

\(\Rightarrow a=\frac{-3}2\)

Also given that x = 1 is a root of equation \(x^2+x+b=0.\)

\(\therefore1^2+1+b=0\)

\(\Rightarrow b=-2\)

Now, ab \(=\frac{-3}2\times-2=3\)

Correct option is A) 3



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