Hello, this equation came up in class:
y^4 - 400y^2 + 25600
The teacher used this method to solve it:
let y^2 = z
z^2 - 400z + 25600
z = 320 or 80
I was just wondering what the name for the method used to solve it is, so that I can google and find out more information / practice examples etc. It is the first time I had come across this type of polynominal with an exponent higher than 3.