Question

If-1 and -2 are the zeroes of ax^3+3x^2-bx-6, find the third zero and the values of a and b

Answer 1

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Ur Ans
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If -1 & -2 are zeroes of the equation
Now put the Value of X = -1

a(-1)^3+3(-1)^2 +b-6 =0
-a +3 +b -6 = 0
-a+b = 3........(1)

Now put X = -2

a(-2)^3 +3(-2)^2 +2b-6 =0
-8a +12 +2b -6 =0

-8a +2b = -6.......(2)

Solve equation (1) & (2)
Substract the equation

-a+b = 3
-8a+2b = -6

In (1) multiply by 2 & (1) by 1

-2a +2b = 6
-8a +2b = -6
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6a = 12
a = 12/6
a = 2

Putting the value of a
-2 +b = 3
B = 3+2
B = 5

A = 2, B= 5 Ans

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