college algebra, Please help!!
posted by ladybug on .
Answer the following function.
f(x)=2x^2x1
A. Is the point (2,9) on the graph of f?
B. If x equals 2, what is fx? What point(S) are on the graph of f?
c. if f(x)= 1, what is x? what point(s) are on the graph of f?
d. what is the domain of f?
e. List the xintercpts, if any, of the graph of f.
f. List the yintercept if any, of the graph of f.
**Can someone please help me with this. I have no idea, i'm lost!!!

Do you realize that
f(x) = 2x^2  x  1 and y = 2x^2  x  1 say the same thing ?
A) sub in the values x = 2 and y  9 and see if they satisfy the equation
LS = 2(2)^2  (2)  1
= 8 + 2 + 1 = 9
RS = 9 = LS
Yes , the point (2,9) does lie on the graph.
B) replace x with 2 and evaluate
C) f(x) = 1 is the same as saying y = 1
so 2x^2  x  1 = 1
2x^2  x = 0
x(2x1) = 0
x = 0 or x = 1/2
the two corresponding points are (0,1) and (1/2, 1)
D) the domain of a function are the values of x that you may use in the equation. Can't we use any x we feel like ? , so the domain is the set of real numbers
E) at the xintercept, y = 0
2x^2  x  1 = 0
(2x + 1)(x  1) = 0
x = 1/2 or x = 1 > the two xintercepts
F) for the yintercept , let x = 0
y = 0  0  1 = 1