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Math Challenge II-B Algebra 5.28

 
 
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Re: Math Challenge II-B Algebra 5.28
by Areteem Professor - Thursday, 16 July 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 $x^7 = x^3 \cdot x^3 \cdot x$.