A Very Simple Problem

Algebra Level 1

x 2 y 2 = 7 x^{2} - y^{2} = 7
z = x y z = x^{y}
x 2 + y 2 = 25 x^{2} + y^{2} = 25
t = x y t = \frac{x}{y}

Find the value of z z .

3 4/3 7 64

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1 solution

Ananth Jayadev
Dec 24, 2015

We are supposed to find the value of z z , which is equal to x y { x }^{ y } . To do this we have to find the values of x x and y y .

First, let us set up the equation x 2 + y 2 + x 2 y 2 = 25 + 7 { x }^{ 2 }+{ y }^{ 2 }+{ x }^{ 2 }-{ y }^{ 2 }=25+7 . This simplifies to 2 x 2 = 32 2{ x }^{ 2 }=32 , then x 2 = 16 { x }^{ 2 }=16 , so x = 4 x=4 .

Then let us solve for the equation 4 2 + y 2 = 25 { 4 }^{ 2 }+{ y }^{ 2 }=25 . We get 16 + y 2 = 25 16+{ y }^{ 2 }=25 , then y 2 = 9 { y }^{ 2 }=9 , and finally y = 3 y=3 .

Finally, let us plug 4 and 3 into the equation z= x y { x }^{ y } . We get z = 4 3 = 4 × 4 × 4 = 64 z={ 4 }^{ 3 }=4 \times 4 \times 4=64 . So z = 64 z=64 .

I suppose that t t is just extra information.

Peter Michael - 5 years, 5 months ago

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Yes, it is a trap which someone might fall into if they don't read the question properly. But everyone here is extremely smart so I doubt anyone fell in the trap.

Ananth Jayadev - 5 years, 5 months ago

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