function problem

[moronatmath]

Given that f(x)=x^2-7 x and g(x)=x + 13, find
(a) f+g=
(b) f-g=
(c) fg=
(d) f/g=

Ok here is my attempt at this problem

f+g= x^2+x-13/7

f-g=x^2-13/7

fg=(x^2-7x)(x+13)

f/g= (x^2-7x)/(x+13)
??? Please help

 

[Guest]

f+g = x^2-7 x + x + 13

= x^2 - 7x +x +13

= x^2 -6x + 13

and do this style for all.

 

[Gene]

Not sure where you went.
f+g = x^2-7x+x+13
No fractions here.

f-g = x^2-7x-(x+13)
No fractions here either. Just combine terms.

fg: looks good but I suspect they want it expanded.

f/g: Ditto. Are you practicing long division? Maybe I'm wrong about expansion.

 

[moronatmath]

ok so f-g i got

f-g=x^2-8x+13

how do I expand (x^2-7x)(x+13) ?

What do I do for "d"?

(x^2-7x)/(x+13) ?

 

[Gene]

Closer.
f-g = x^2-7x-(x+13) =
x²-8x-13

I was thinking they would want it multiplied and divided out but I don't know. If they do
c) would be
x³+6x²-91x

d) would be
x-20+260/(x+13)

If all you are doing is learning functions, leave them as you have them.

 

[moronatmath]

ok so I think I am just doing functions.

for b... x^2-7x-x-13 is the correct way to set up the function, and x^2-6x+13 is incorrect? I don't really understand why? Why would I manipulate the function g?

 

[Gene]

Because it is minus g(x). g(x) = x+13
-g(x) = -(x+13) = -x-13
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Gene