## anonymous 4 years ago can someone check and see if this is right?

1. anonymous

$\int\limits_{?}^{?}(1+4x)/(\sqrt{1+x+2x ^{2}}dx$

2. anonymous

i got $.5\ln \left| \sqrt{1+x+2x ^{2}} \right| +c$

3. Rogue

$u = 1 + x + 2x^2, du = (1 + 4x) dx$

4. anonymous

it looks wrong

5. Rogue

There is no log. Instead it is $2 \sqrt{ 1 + x +2x^2}$

6. anonymous

why could you not use ln

7. Rogue

well, the integral becomes $\int\limits_{}^{} \frac {du}{u^.5}$

8. Rogue

$\int\limits_{}^{} = u^{-.5}du$

9. anonymous

$\int\limits \frac{f'(x)}{f(x)}dx=lnf(x)$

10. Rogue

oops. There isn't supposed to be an equal sign in the integral.

11. anonymous

ok i think i got it

12. Rogue

Alright, just the use power rule for integration to solve.

13. anonymous

thanks