You know f(x)= ax² + bx + c. Well when you get the equations why is it always like:

Question

1) a + b + c = something
2) 4a + 2b + c = something
3) 9a + 3b + c = something

I mean why is the first one always 'a+b+c'? etc.

Also does it have to be f(x) or can it be f(n) instead?

Thanks :) Sorry if my questions don't make sense!

The first one is always NOT a + b+ c, it usually is not.

f(x) is a silly convention of using x for the unknown. It is just historical convention that x, and y, and z are often variables. If you feel a need, be different, and use other symbols.
example:
f(@)= @^2 + 4*@
Machts nichts. However, your classmates may think you weird, and you may cease to get invitations to math parties. You may even fail to marry well. Such is the result of failing to follow conventions.

I like your questions, they are so basic they challenge the roots of our structured usages. Keep thinking.

Ok you're weird. I bet you get invited to loads of maths parties...

2x+y=1
3x-2y=5

2* (2x+y=1)= 4x+2y=2
3x-2y=5
y=4x-3x= x
5-2= 3

5m-2n=13
m-2n=1

can someone please help me with this??

5x + 3y = 9
7x + 8y = 5

help please!

11p + 3q = 71
5p - q = 37

8-3-2+777-7666=fr4kffdxld erpowed-r