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# Integration of Irrational Functions JEE Notes | EduRev

## JEE : Integration of Irrational Functions JEE Notes | EduRev

The document Integration of Irrational Functions JEE Notes | EduRev is a part of the JEE Course Mathematics (Maths) Class 12.
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Integration of Irrational Functions

Certain types of integrals of algebraic irrational expressions can be reduced to integrals of rational functions by a appropriate change of the variable. Such transformation of an integral is called its rationalization.

(i) If the integrand is a rational function of fractional powers of an independent variable x, i.e. the function Rthen the integral can be rationalized by the substitution x = tm, where m is the least common multiple of the numbers q1, q2, ...., qk.

(ii) If the integrand is a rational function of x and fractional powers of a linear fractional function of the form  then rationalization of the integral is effected by the substitution  where m has the same sense as above.

Ex.68 Evaluate

Sol.

Rationalizing the denominator, we have

Ex.69 Evaluate I =

Sol. The least common multiple of the numbers 3 and 6 is 6, therefore we make the substitution

x = t6, dx = 6t5 dt.

Ex.70 Evaluate I =

Sol. The integrand is a rational function of  therefore we put 2x – 3 = t6, whence

Returning to x, we get

Ex.71 Evaluate

Sol.

Let x = t3 ⇒ dx = 3t2 then

Ex.72 Evaluate I =

Sol. The integrand is a rational function of x and the expression   therefore let us introduce the substitution

INTEGRAL OF THE TYPE   WHERE X AND Y ARE LINEAR OR QUADRATIC EXPRESSION

Ex.73 Integrate

Sol.

Put 4x + 3 = t2, so that 4dx = 2tdt and (2x + 1)

Ex.74 Evaluate

Sol.

Put (x + 2) = t2, so that dx = 2t dt, Also x = t– 2.

∴

dividing the numerator by the denominator

Ex.75 Integrate

Sol.

Put (x + 1) = t2, so that dx = 2t dt. Also x = t2 – 1.

Ex.76 Integrate

Sol.

Put (1 + x) = 1/t, so that dx = – (1/t2) dx.

Also x = (1/t) – 1.

Ex.77 Evaluate

Sol.

Put x = 1/t, so that dx = – (1/t2) dt.

∴

Now put 1 + t2 = z2 so that t dt = z dz. Then

[∵ t = 1/x]

Ex.78 Evaluate I =

Sol.

Integration Of A Binomial Differential

The integral  where m, n, p are rational numbers, is expressed through elementary functions only in the following three cases :

Case I : p is an integer. Then, if p > 0, the integrand is expanded by the formula of the binomial; but if p < 0, then we put x = tk, where k is the common denominator of the fractions and n.

Case II : is an integer. We put a + bxn = tα, where α is the denominator of the fraction p.

Case III :+ p is an integer we put a + bxn = tαxn, where a is the denominator of the fraction p.

Ex.79 Evaluate I =

Sol.

Here p = 2, i.e. an integer, hence we have case I.

Ex.80 Evaluate I =

Sol.

i.e. an integer.we have case II. Let us make the substitution. Hence ,

Ex.81 Evaluate I =

Sol.

Here p = – 1/2 is a fraction, m+1/2 = -5/2 also a fraction, but m+1/n + p/2 = -5/2 -1/2 = -3 is an integer, i.e. we have case III, we put 1 + x4 = x4/2,

Hence

Substituting these expression into the integral, we obtain

Returning to x, we get I =

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## Mathematics (Maths) Class 12

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