Online Course Discussion Forum

Return to: Site

Math Challenge II-B Algebra 5.28

 
 
Picture of James Shi
Math Challenge II-B Algebra 5.28
by James Shi - Thursday, July 16, 2020, 11:44 AM
 

After thinking about the problem for a while, I still do not know what to do for 5.28. I feel like it has something to do with the difference of cubes since x^3 and 8 are both cubes. Are there any strategies that I could try? Thank you.

 
Picture of Areteem Professor
Re: Math Challenge II-B Algebra 5.28
by Areteem Professor - Thursday, July 16, 2020, 1:01 PM
 

Here you can "reduce the exponents" of the target expression. Since we know $x^3 + 4x = 8$, we have that $x^3 = 8 - 4x$. You can then use this to rewrite some portions of the target expression. Note that $x^7 = x^3 \cdot x^3 \cdot x$.

 
Show parent