Systems of equations with one inequality and exponents. The equation is this: 8000 <

Carolyn Beck

Carolyn Beck

Answered question

2022-06-10

Systems of equations with one inequality and exponents.
The equation is this:
8000 < x y 5 < 8100
x y 4 x y 3 > 5000
I have no idea how to solve for the greater then or less then part of the equation. I also have no idea how to solve for exponents and finally if it even can be solved!

Answer & Explanation

Govorei9b

Govorei9b

Beginner2022-06-11Added 21 answers

The system you have is not solvable.
Since we don't know the exact values of x y 5 and x y 4 x y 3 , let's put in some values, say r and s, and see what happens. We have:
(1) x y 5 = r
(2) x y 4 x y 3 = s
8000 < r < 8100
s > 5000
We know that y 0, since otherwise r would equal zero, contradicting the fact that r > 8000 > 0. Thus, from (1), we can find
(3) x = r y 5
Substituting (3) into (2) gives
r y 1 r y 2 = s
which we can multiply by y 2 to get
r y r = s y 2
(4) 0 = s y 2 r y + r
I'm not sure if you're familiar with the quadratic equation, but we can use the discriminant to tell when (4) will have solutions. Specifically, (4) will have (real) solutions when
r 2 4 r s > 0
But, we know that s > 5000, so
r 2 4 r s < r 2 4 r ( 5000 )
r 2 4 r s < r ( r 20000 )
But, for 8000 < r < 8100, the right hand side is always negative, so our discriminant is always less than zero, and we have no real solutions.

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