Basic of Logarithms
easy

The partial fractions of ${{3{x^3} - 8{x^2} + 10} \over {{{(x - 1)}^4}}}$ is

A

${3 \over {(x - 1)}} + {1 \over {{{(x - 1)}^2}}} + {7 \over {{{(x - 1)}^3}}} + {5 \over {{{(x - 1)}^4}}}$

B

${3 \over {(x - 1)}} + {1 \over {{{(x - 1)}^2}}} - {7 \over {{{(x - 1)}^3}}} + {5 \over {{{(x - 1)}^4}}}$

C

${3 \over {(x - 1)}} + {1 \over {{{(x - 1)}^2}}} - {7 \over {{{(x - 1)}^3}}} + {5 \over {{{(x - 1)}^4}}}$

D

None of these

Solution

(c) ${{3{x^3} – 8{x^2} + 10} \over {{{(x – 1)}^4}}} = {A \over {x – 1}} + {B \over {{{(x – 1)}^2}}} + {C \over {{{(x – 1)}^3}}} + {D \over {{{(x – 1)}^4}}}$

==>$3{x^3} – 8{x^2} + 10 = A{(x – 1)^3} + B{(x – 1)^2} + C(x – 1) + D$

Equating coefficients of different powers of $x$, $3 = A$

$ – 8 = – 3A + B \Rightarrow B = 1$

$0 = 3A – 2B + C \Rightarrow C = – 7$

$10 = – A + B – C + D \Rightarrow D = 5$

$\therefore$ Given expression

= ${3 \over {x – 1}} + {1 \over {{{(x – 1)}^2}}} – {7 \over {{{(x – 1)}^3}}} + {5 \over {{{(x – 1)}^4}}}$.

Std 11
Mathematics

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