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For x>ex > e, ∫dxx−x\int \frac{dx}{x - \sqrt{x}} is equal to

Solution

✅ Correct Option: 4

Looking at the denominator x−xx - \sqrt{x}, factor out x\sqrt{x}:

x−xx - \sqrt{x}

=x⋅x−x= \sqrt{x} \cdot \sqrt{x} - \sqrt{x}

=x(x−1)= \sqrt{x}(\sqrt{x} - 1)

The integral becomes:

∫dxx(x−1)\int \frac{dx}{\sqrt{x}(\sqrt{x} - 1)}


Let u=xu = \sqrt{x}

Then x=u2x = u^2 and dx=2u dudx = 2u \, du

Substituting:

∫2u duu(u−1)\int \frac{2u \, du}{u(u - 1)}


Canceling uu from numerator and denominator:

∫2u duu(u−1)\int \frac{2u \, du}{u(u - 1)}

=∫2 duu−1= \int \frac{2 \, du}{u - 1}


Using the standard integral formula ∫1u−1du=ln⁡∣u−1∣+C\int \frac{1}{u-1} du = \ln|u-1| + C:

∫2 duu−1\int \frac{2 \, du}{u - 1}

=2ln⁡∣u−1∣+C= 2 \ln|u - 1| + C


Substituting back u=xu = \sqrt{x}:

2ln⁡∣x−1∣+C2 \ln|\sqrt{x} - 1| + C

Therefore, ∫dxx−x=2log⁡e∣x−1∣+C\int \frac{dx}{x - \sqrt{x}} = 2 \log_e |\sqrt{x} - 1| + C

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