Question

ОЧЕЕЕЕЕНЬ СРОЧНО, ПОМОГИТЕ ПАЗЯЗЯ!!
1)int x^2dx/x^4+5x^2 +4

2)int x arctg2xdx

3)int dx/(x+1) sqrt 1-x-x^2

4)int sin^3 5xdx

5)int 5sqrtx -2x^3 +4/x^2 .dx

6)int 2x+3/sqrt 2x^2-x+6

Answer 1

$2)\; \; \int x\cdot arctg2x\, dx=[\, u=arctg2x,\; du=\frac{2\, dx}{1+4x^2},\; dv=x\, dx,\; v=\frac{x^2}{2}\, ]=\\\\=\frac{x^2}{2}\cdot arctg2x-\int \frac{x^2\, dx}{1+4x^2}=\frac{x^2}{2}\cdot arctg2x-\frac{1}{4}\int \frac{x^2\, dx}{x^2+\frac{1}{4}}=\\\\=\frac{x^2}{2}\cdot arctg2x-\frac{1}{4}\int (1-\frac{1}{4}\cdot \frac{1}{x^2+\frac{1}{4}})dx=\\\\=\frac{x^2}{2}\cdot arctg2x-\frac{1}{4}x+\frac{1}{16}\cdot 2\, arctg\, 2x+C\; ;$

$3)\; \; \int \frac{dx}{(x+1)\sqrt{1-x-x^2}}=[\, x+1=\frac{1}{t},\; x=\frac{1}{t}-1,\; dx=-\frac{dt}{t^2}\, ]=\\\\=-\int \frac{dt}{t^2\cdot \frac{1}{t}\cdot \sqrt{1-\frac{1}{t}+1-\frac{1}{t^2}+\frac{2}{t}-1}}=-\int \frac{dt}{\sqrt{t^2+t-1}}=-\int \frac{dt}{\sqrt{(t+\frac{1}{2})^2-\frac{5}{4}}}=\\\\=-\int \frac{d(t+\frac{1}{2})}{\sqrt{(t+\frac{1}{2})^2-\frac{5}{4}}}=-ln\Big |t+\frac{1}{2}+\sqrt{t^2+t-1}\Big |+C=\\\\=-ln\Big |\frac{1}{x+1}+\frac{1}{2}+\sqrt{\frac{1}{(x+1)^2}+\frac{1}{x+1}-1}\Big |+C\; ;$

$6)\; \; \int \frac{(2x+3)dx}{\sqrt{2x^2-x+6}}=\int \frac{(2x+3)dx}{\sqrt{2\cdot (\, (x-\frac{1}{4})^2+\frac{47}{16})}}=[\, t=x-\frac{1}{4},\; x=t+\frac{1}{4},\; dx=dt\, ]=\\\\=\frac{1}{\sqrt2}\int \frac{(2t+3,5)dt}{\sqrt{t^2+\frac{47}{16}}}=\frac{1}{\sqrt2}\int \frac{2t\, dt}{\sqrt{t^2+\frac{47}{16}}}+\frac{3,5}{\sqrt2}\int \frac{dt}{\sqrt{t^2+\frac{47}{16}}}=\\\\=\frac{1}{\sqrt2}\cdot 2\, \sqrt{t^2+\frac{47}{16}}+\frac{7}{2\sqrt2}\cdot ln\Big |t+\sqrt{t^2+\frac{47}{16}}\Big |+C=$

$=\sqrt2\cdot \sqrt{x^2-\frac{x}{2}+3}+\frac{7}{2\sqrt2}\cdot ln\Big |x-\frac{1}{4}+\sqrt{x^2-\frac{x}{2}+3}\, \Big |+C\; .$