If x 3 ( 2 x - 1 ) ( x - 1 ) 2 = A + B 2 x - 1 + C x - 1 + D ( x - 1 ) 2 , then 2 A - 3 B + 4 C + 5 D =

If x3(2x-1)(x-1)2=A+B2x-1+Cx-1+D(x-1)2, then 2A-3B+4C+5D=
  1. 212
  2. 232
  3. 14
  4. 192

Solution

We have,x3(2x-1)(x-1)2=A+B2x-1+Cx-1+Dx-12

Now,

Dr=(2x-1)(x-1)2

     =(2x-1)(x2-2x+1)

       =2x3-5x2+4x-1

Now,

x3(2x-1)(x-1)2=122x3(2x-1)(x-1)2

                                =122x3-5x2+4x-1+5x2-4x+1(2x-1)(x-1)2

 =121+5x2-4x+1(2x-1)(x-1)2

=12+125x2-4x+1(2x-1)(x-1)2  ...i

Now,

5x2-4x+12x-1x-12=B2x-1+Cx-1+Dx-12

5x2-4x+1x-12=B+2x-1Cx-1+Dx-12  Putting x=12 we get B=1.

Again,

5x2-4x+12x-1x-12=B2x-1+Cx-1+Dx-12

5x2-4x+12x-1=x-12×B2x-1+x-1C+D

Putting x=1, we get D=2.

Now, considering the actual expression, we have

x3(2x-1)(x-1)2=A+B2x-1+Cx-1+Dx-12

Putting x=0, we get

A-B-C+D=0

12-1-C+2=0

C=32

Now,

2A-3B+4C+5D

212-3×1+432+5×2=14

Asked in: AP EAMCET 2018 (25 Apr Shift 1)

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