simple SAT question. confused.

Question

sat question

My friend selected option B, I did C. We're confused. Can someone please explain this for my friend?

Your friend has not got a perfect score me thinks.. – Chinny84 Jun 25 '15 at 15:57 — Chinny84, Jun 25 '15 at 15:57

score 1 · Answer 1 · answered Jun 25 '15 at 15:45

1

No doubt Option $\,\,\,\,C\,\,\,\,\,$

Note that $a^{m+n}=a^m \cdot a^n$

Observe that \begin{align} (2x)^{3y}-(2x)^{y} \\= (2x)^{y+2y}-(2x)^{y}\\=(2x)^{y}[(2x)^{2y}-1] \end{align}

answered Jun 25 '15 at 15:45

A.D

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score 1 · Answer 2 · answered Jun 25 '15 at 16:19

Option C is correct obviously because we can see that \begin{align} (2x)^{3y}-(2x)^{y} \\= (2x)^{y+2y}-(2x)^{y}\\=(2x)^{y}[(2x)^{2y}-1] \end{align} Option B is wrong because if we take out $\ 2^y $ common then we will get $\ 2^y{[2^{2y} . x^{3y}-x^y}]$

simple SAT question. confused.

2 Answers2