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Question
If x = 1 is a common roots of the equations ax2 + ax + 3 = 0 and x2 + x + b = 0, then ab =
Options
3
3.5
6
-3
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Solution
x = 1is the common roots given quadric equation are `ax^2 + ax + 3 = 0`, and `x^2 + x + b= 0`
Then find the value of q.
Here, `ax^2 + ax + 3 = 0 `….. (1)
`x^2 + x + b = 0`….. (2)
Putting the value of x = 1 in equation (1) we get
`a xx 1^2 + a xx 1 +3 = 0`
`a+a + 3 = 0`
`2a = -3`
`a = -3/2`
Now, putting the value of x = 1 in equation (2) we get
`1^2 + 1+b = 0`
`2 +b = 0`
`b = -2`
Then,
`ab = (-3)/2 xx (-2)`
`=3`
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