SOLUTION: Hi, I've been trying for hours to figure out how to isolate y in the following equation. y(y-5)=546 I know y=26 but how do I prove/solve it? (I've come up with numerous vari

Question 9072: Hi, I've been trying for hours to figure out how to isolate y in the following equation.
y(y-5)=546
I know y=26 but how do I prove/solve it? (I've come up with numerous variations to the equation such as: 8y-40=4368/y, (8y-40)y=4368, y^2-5y=546, etc). Thanks in advance for your help.
Peter
Answer by xcentaur(357) (Show Source): You can put this solution on YOUR website!
y(y-5)=546
y^2 -5y -546 = 0
This gives us the roots 26 and -21.
The working is shown below.

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=2209 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 26, -21. Here's your graph:

Hope this helps,
Prabhat

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