# Find all real-number solutions...

• Apr 23rd 2008, 05:28 AM
mt_lapin
Find all real-number solutions...
Can somebody please explain to me why the answer to $\displaystyle 5b^4=194$ is ±2.5 and not just 2.5 and why the answer to $\displaystyle \frac{b^7}{b^4}=\frac{75}{4}$ is 2.66 and not ±2.66 ?

Hopefully you understand where my confusion is... it's about ± and when it should and shouldn't be used.
• Apr 23rd 2008, 05:35 AM
mr fantastic
Quote:

Originally Posted by mt_lapin
Can somebody please explain to me why the answer to $\displaystyle 5b^4=194$ is ±2.5 and not just 2.5 and why the answer to $\displaystyle \frac{b^7}{b^4}=\frac{75}{4}$ is 2.66 and not ±2.66 ?

Hopefully you understand where my confusion is... it's about ± and when it should and shouldn't be used.

Substitute the negtaive solutions into the equation. Do they work? Why ....? What happens when a negative number gets raised to an even power ....? Would the same thing happen if you raised a negtaive number to an odd power ....?