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If ∫x4x−2dx=px+qx2+rx3+sx4+tlog⁡∣x−2∣+C\int \frac{x^4}{x-2}dx = px + qx^2 + rx^3 + sx^4 + t\log |x - 2| + C, where C is an arbitrary constant and p, q, r, s, t are real numbers, then the correct arrangement of p, q, r, s, t is:

Solution

✅ Correct Option: 4

To integrate ∫x4x−2 dx\int \frac{x^4}{x-2} \, dx, substitute u=x−2u = x - 2, which means x=u+2x = u + 2 and dx=dudx = du.

  1. Expand the numerator:

x4=(u+2)4=u4+4(u3)(2)+6(u2)(4)+4(u)(8)+16x^4 = (u + 2)^4 = u^4 + 4(u^3)(2) + 6(u^2)(4) + 4(u)(8) + 16

x4=u4+8u3+24u2+32u+16x^4 = u^4 + 8u^3 + 24u^2 + 32u + 16

  1. Divide by uu and integrate:

∫u4+8u3+24u2+32u+16u du=∫(u3+8u2+24u+32+16u)du\int \frac{u^4 + 8u^3 + 24u^2 + 32u + 16}{u} \, du = \int \left( u^3 + 8u^2 + 24u + 32 + \frac{16}{u} \right) du

=u44+8u33+12u2+32u+16log⁡∣u∣+C1= \frac{u^4}{4} + \frac{8u^3}{3} + 12u^2 + 32u + 16\log|u| + C_1

  1. Substitute u=x−2u = x - 2 back into the expression:
  • 14(x−2)4=14(x4−8x3+24x2−32x+16)\frac{1}{4}(x-2)^4 = \frac{1}{4}(x^4 - 8x^3 + 24x^2 - 32x + 16)
  • 83(x−2)3=83(x3−6x2+12x−8)=83x3−16x2+32x−643\frac{8}{3}(x-2)^3 = \frac{8}{3}(x^3 - 6x^2 + 12x - 8) = \frac{8}{3}x^3 - 16x^2 + 32x - \frac{64}{3}
  • 12(x−2)2=12(x2−4x+4)=12x2−48x+4812(x-2)^2 = 12(x^2 - 4x + 4) = 12x^2 - 48x + 48
  • 32(x−2)=32x−6432(x-2) = 32x - 64
  1. Group the terms by powers of xx (absorb constants into CC):
  • Coefficient of x4x^4 (ss): 14=0.25\frac{1}{4} = 0.25
  • Coefficient of x3x^3 (rr): −2+83=23≈0.67-2 + \frac{8}{3} = \frac{2}{3} \approx 0.67
  • Coefficient of x2x^2 (qq): 6−16+12=26 - 16 + 12 = 2
  • Coefficient of xx (pp): −8+32−48+32=8-8 + 32 - 48 + 32 = 8
  • Coefficient of log⁡∣x−2∣\log|x-2| (tt): 1616
  1. Compare the values:

t(16)>p(8)>q(2)>r(0.67)>s(0.25)t(16) > p(8) > q(2) > r(0.67) > s(0.25)

Thus, the correct arrangement is t>p>q>r>st > p > q > r > s.

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