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kadence
11-08-2013, 04:34 AM
Which of the following is equal to (x^4)^5+(y^4) (y^5) ?

(A) x^{20} \cdot y^9

(B) x^9+y^{20}

(C) x^{20}+y^{20}

(D) x^9+y^9

(E) x^{20}+y^9

Thanks!;);)

elizabeth
11-08-2013, 04:35 AM
Properties of exponents

(x^m)^n=x^{mn}

x^m x^n =x^{m+n}

So, our expression is equal to

(x^4)^5+(y^4) (y^5)=x^{4\cdot5}+y^{4+5}= x^{20}+y^{9}

Therefore the correct answer is (E).

kadence
11-08-2013, 04:37 AM
Thanks Elisabeth!