# Thread: Graph work again!

1. ## Graph work again!

im stuck on this question:
a. draw the graph of y=3x-6
b. draw the inverse aswell
c. what is y=3x and its inverse symmetrical about?
d. what do you notice about the line of symmetry?
im stuck on c and d can someone(if possible) pleez explain it in SIMPLE language coz im only in yr9!
thankyou

2. Originally Posted by help_me
im stuck on this question:
a. draw the graph of y=3x-6
to draw a line, all you need are two points. the x- and y-intercepts are usually good points, especially since you only have to find one of them (the y-intercept is given by the lone constant, so we don't have to calculate it).

for the x-intercept, set y = 0

=> 0 = 3x - 6
=> x = 2

thus, our y-intercept is (0,-6) and our x-intercept is (2,0)

so plot those points on a pair of axis and draw a straight line through them and you're done. see below

b. draw the inverse aswell
to find the inverse function of y = f(x), we switch x and y and solve for y.

thus for the inverse of y = 3x - 6, we solve: x = 3y - 6 for y.

=> y = (1/3)x + 2 is the inverse function.

graph this the same way i did the other.

c. what is y=3x and its inverse symmetrical about?
for any graph that has an inverse, the graph and it's inverse is symmetrical about the line y = x.

d. what do you notice about the line of symmetry?
i leave this question to you. after drawing the graphs, you tell me

3. ## oh...........

thank you so much for explaining it so clearly!

4. for the x-intercept, set y = 0

=> 0 = 3x - 6
=> x = 2

That's cool and easy! I never knew that.
I always plugged in coordinates (1,1) to find the 'y' intercept and for some reason I don't remember what I did next.
It wasn't as easy as that though.