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Evaluate: ∫5x2+20x+6x3+2x2+x dx

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प्रश्न

Evaluate: `int (5"x"^2 + 20"x" + 6)/("x"^3 + 2"x"^2 + "x")` dx

योग
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उत्तर

Let I = `int (5"x"^2 + 20"x" + 6)/("x"^3 + 2"x"^2 + "x")` dx

`= int (5"x"^2 + 20"x" + 6)/("x"("x"^2 + 2"x" + 1))` dx

`= int (5"x"^2 + 20"x" + 6)/("x"("x + 1")^2)` dx

Let `(5"x"^2 + 20"x" + 6)/("x"("x + 1")^2) = "A"/"x" + "B"/"x + 1" + "C"/("x + 1")^2`

∴ 5x2 + 20x + 6 = A(x + 1)2 + B(x + 1)x + Cx   ...(i)

Putting x = 0 in (i), we get

5(0) + 20(0) + 6 = A(1)2 + B(1)(0) + C(0)

∴ A = 6

Putting x = - 1 in (i), we get

5 (1) + 20(- 1) + 6 = A (0)+ B (0) (- 1) + C (-1)

∴ - 9 = - C

∴ C = 9

Putting x = 1 in (i), we get

5 (1) + 20 (1) + 6 = A (2)2 + B (2) (1) + C (1)

∴ 31 = 4A + 2B + C

∴ 31 = 4(6) + 2B + 9

∴ B = - 1

∴ `(5"x"^2 + 20"x" + 6)/("x"("x + 1")^2) = 6/"x" + (-1)/"x + 1" + 9/("x + 1")^2`

∴ I = `int [6/"x" + (- 1)/"x + 1" + 9/("x + 1")^2]` dx

`= 6 int 1/"x" "dx" - int 1/"x + 1" "dx" + 9 int ("x + 1")^-2` dx

`= 6 log |"x"| - log |"x + 1"| + 9("x + 1")^-1/(-1)` + c

∴ I = `6 log |"x"| - log |"x + 1"| - 9/("x + 1")` + c

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अध्याय 5: Integration - EXERCISE 5.6 [पृष्ठ १३५]

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बालभारती Mathematics and Statistics 1 (Commerce) [English] Standard 12 Maharashtra State Board
अध्याय 5 Integration
EXERCISE 5.6 | Q 8) | पृष्ठ १३५

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