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Jack
10-10-2013, 11:40 AM
Find xy If z=x^7=y^4 and z is a positive real number.

(A) z^{28}
(B) z^{11}
(C) z^{1/28}
(D) z^{11/28}

Thanks

miranda
10-10-2013, 11:41 AM
First we solve for x : z=x^7 \Rightarrow x=z^{\frac{1}{7}} in terms of z

then we solve for y : z=x^7 \Rightarrow x=z^{\frac{1}{4}} in terms of z

So, xy= z^{\frac{1}{7}} z^{\frac{1}{4}}= z^{\frac{1}{7}+\frac{1}{4}}= z^{\frac{4+7}{28}}= z^{\frac{11}{28}}


Hope these help

Jack
10-10-2013, 11:42 AM
Thanks Miranda!