What is the integral of x^3sqrt(x^2-7) ?

The integral of x^3sqrt(x^2-7) is 1/5 (x^2-7)^{5/2}+7/3 (x^2-7)^{3/2}+C

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integral of x^3sqrt(x^2-7)

\int x^{3} x^{2} - 7 d x

\frac{1}{5} (x^{2} - 7)^{\frac{5}{2}} + \frac{7}{3} (x^{2} - 7)^{\frac{3}{2}} + C

Solution steps

\int x^{3} x^{2} - 7 d x

Apply u-substitution

= \int (u^{2} + 7) u^{2} d u

Expand

(u^{2} + 7) u^{2} : u^{4} + 7 u^{2}

= \int u^{4} + 7 u^{2} d u

Apply the Sum Rule:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \int u^{4} d u + \int 7 u^{2} d u

\int u^{4} d u = \frac{u ^{5}}{5}

\int 7 u^{2} d u = \frac{7 u ^{3}}{3}

= \frac{u ^{5}}{5} + \frac{7 u ^{3}}{3}

Substitute back

u = x^{2} - 7

= \frac{( x ^{2} - 7 ) ^{5}}{5} + \frac{7 ( x ^{2} - 7 ) ^{3}}{3}

Simplify

\frac{( x ^{2} - 7 ) ^{5}}{5} + \frac{7 ( x ^{2} - 7 ) ^{3}}{3} : \frac{1}{5} (x^{2} - 7)^{\frac{5}{2}} + \frac{7}{3} (x^{2} - 7)^{\frac{3}{2}}

= \frac{1}{5} (x^{2} - 7)^{\frac{5}{2}} + \frac{7}{3} (x^{2} - 7)^{\frac{3}{2}}

Add a constant to the solution

= \frac{1}{5} (x^{2} - 7)^{\frac{5}{2}} + \frac{7}{3} (x^{2} - 7)^{\frac{3}{2}} + C

What is the integral of x^3sqrt(x^2-7) ?
The integral of x^3sqrt(x^2-7) is 1/5 (x^2-7)^{5/2}+7/3 (x^2-7)^{3/2}+C