if (1+ax +bx2)(1-2x)18 be expressed in ascending powers of x such that coefficient of x3 and x4 are 0 then (a,b)is equal to :

a) (16,272/3) b) (4,44/3)

c)(1/16,88/3)

The given expression can be express by binomial theorem as follow

 

 

It is given that the coefficients of are zero. Therefore we have

 

 

Now, we will add the equation (1) and equation (2), we get

 

 

From equation (2), we have

 

 

Hence, the correct option is (a )

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