i need more help

[Guest]

Ihave four questions:
1. Solve the euation 5y+10x=30 for y i got the answer y=-2+6 is this right?
2. Solve the equation 4x-2y=-12for y I got -2x +6 is this right?
3. If f(x)=2x^2-5,f(5)= what I can not get this at all I had 15 and that was wrong?
4. multiply (5b-7)(5b+7) I have it figured out that it is 25b^2-49 is this right?
Thanks forall your help

 

[Gene]

1. Solve the equation 5y+10x=30 for y. I got the answer y=-2+6 is this right?
sorta, but you lost the x.
y=-2x+6

2. Solve the equation 4x-2y=-12for y I got -2x +6 is this right?
You slipped on this one. The numbers are right but the signs are wrong.

3. If f(x)=2x^2-5,f(5)= what I can not get this at all I had 15 and that was wrong?
f(5) means replace x with 5, so you get
f(5) = 2*(5^2)-5
I can't guess what you did wrong to get 15.

4. multiply (5b-7)(5b+7) I have it figured out that it is 25b^2-49 is this right?
Exactly right. Good one.