Question

If x=1 is a common root of equation ax2+ax+3=0 and x2+x+b=0

then ab=

a) 3 b)3.5 c)6 d)-3

Answer 1

right answer is d(-3)

Answer 2

Answer

Given x=1 is a common root of both the equation then

putting x=1 in ax²+ax+3

a(1)²+a(1)+3=0

a+a+3=0

2a+3=0

2a= - 3

a= -3/2

Now in x²+x+b

1+1+b=0

2+b=0

b= - 2

Now , ab = - 3/2 * - 2/1 =6/2 =3

ab=3 ans