Are My Math Solutions Correct?

[qdv]

Hi i am new here, and just wondering if my answers are right, please check for me.

1. Evaluate g(x) = x^2 + x
g(x + 3)
my answer: x^2 + 7x -12

2. Function or not:
x^2 = y - 3
I say not a function.

3. y^2 = x - y
I would say yes this is a function.

thanks a lot

 

[quasar987]

1. why minus 12 and not plus 12?

2. x(y) is not a function but y(x) is a function.

3. x(y) is a function. Although you cannot re-write this expression as a function y of x, you can see from the graph of x(y) that to each x correspond two different y. This means, by the definition of a function that y(x) is not a function.

reply if you want further explanations.

 

[HallsofIvy]

2. WHY would you say it is not a function?

3. WHY would you say it is a function?

Crucial to answering both those questions: what is the DEFINITION of "function"?

 

[qdv]

for the first one I figured it out to plus 12 also, but when I check the solution it is -12, so i guess the book is wrong. I understand about function now thanks