Question 39419
y=2x+3
This is an equation of a line
We need to find 2 points to draw the line. 
Find The y intercept and x intercept

if x is 0 y = 3
y=3 is the y intercept

if y is 0 x= -3/2
x=-3/2 is the x intercept

By joining the 2 points together you will find the line

y=x^2 + 3
This is an equation of a parabola.
y=ax^2+bx+c
Here a=1 b=0 c=3

a=1>0 the parabola opens upwards
The coordinates of the minimum point are
x=-b/2a = 0/2 =0

y(0)=0^2+3 y = 3

we need 2 more points to draw the parabola.

x=1 y=-4
x=-1 y = 4

Join the tree points together and you see the parabola

y=3x
This is the equation of a line that passes through the point O of the axis

y=ax

We need 1 more point to draw the line

x=1 y=3

Join point O and this point (x=1 y=3) we have the line.

{{{graph( 400, 400, -10, 10, -10, 10, 3x, 2x+3, x^2+3 )}}}