## watermelon26 3 years ago Solve sqrt(x^2 + 4) = 4x

1. thomasj

square both sides

2. thomasj

$x^{2}+4=16x ^{2}$

3. thomasj

can you solve this?

4. RedPrince

$\sqrt(x^2+4)=4x$ taking square on both sides $x^2-4=16x^2$ $16x^2-x^2=4$ $15x^2=4$ $x^2=4/15$ $x=\pm2/\sqrt(15)$

5. pfenn1

@RedPrince, how did you go from$x ^{2}+4=16x ^{2}$to$x ^{2}-4=16x ^{2}$?

6. RedPrince

@pfenn1 by mistake correct it it is now 17 instead of 15 thanks for this