Portions of the graph of f and g are shown above. Which of the following could be a portion of the graph fg?
Graph f is positive and slightly curvy has point 1,1 and -1,-1
Graph g is negative straight line has point -1,1 and 1,-1
The answer is A which is a parabola upside down center at origin. Their 2 ends are 1,-1 and -1,-1
Why is this one is the correct one ?
Thank you
@Adeleloveshiro The graph of g is represented by g(x) = -x.
I have no idea what the graph of f looks like. “Slightly curvy” is a poor descriptor. Given what you said as the answer to the problem, I could figure out what it looks like to some confidence…
However you do know that if f(x) contains the point (1,1) and g(x) contains the point (1,-1), then the graph of f(x)g(x) must contain the point (1,-1). Similarly, f(x)g(x) must contain the point (-1,-1).
Also, you posted this in the AP subforum.
Sorry, are there any way i can show you picture. Like i mean email or fb or line.
It is a lot clearer than description
Back to topic
How do know which pair of points to multiply to which each f and g has 2 points.
If you multiply f(x) (1,1) with g(x) (1,-1)
You get fg ( 1,-1)
The remaining point lefted is f(x) (-1,-1)
and g(x) (-1,1)
And you get fg (1,-1)
-1×-1 = 1
-1×1=-1
Its the same point.
???
@Adeleloveshiro Image probably not needed.
No. Reread what I posted earlier.
fg(x) is sometimes used as shorthand for f(x)*g(x). I generally use the latter but if you see fg(…) where f and get are functions, now you know what it is.
Your description tells me that f(-1) = -1 and g(-1) = 1. Then fg(-1) = -1*1 = -1, i.e. (-1,-1) is a point on fg(x).
Thanks a lot. Now i got it
