Question

Explain me this:

U²-(6/7)u+(1-7)+V²=0

Becomes,
(U-(3/7))²+V²= (4/49)-(1/7)

I can't figure out this...

Answer 1

It is called completing the square.

For example if you have x^2 + bx, you can complete the square as follows:
x^2 + bx = (x + b/2)^2 - (b/2)^2
You can expand the terms on the right and simplify to verify the right hand side is same as the left hand side.

Answer 2

Here you have U^2 - (6/7)U
Take the coefficient of U and divide it by 2. That is the term that will go inside the square:
-6/7 divided by 2 = -3/7
U^2 - (6/7)U = (U - 3/7)^2 - (-3/7)^2

Answer 3

Thank you!!! :)

Answer 4

you are welcome.