How do you graph #y=4x-1# by plotting points?

1 Answer
Mar 2, 2017

Answer:

See explanation

Explanation:

For a strait line graph you technically only need two points. It is better to have 3 or more. I would suggest 3. The logic behind this is that if all the points do not line up when you draw a line through them then you have a wrong calculation some ware.

You may chose to determine what is called critical points and use those (just 2) or you may chose substituting values for #x#

#color(blue)("Choosing substitution")# ( I am using just two points as this is a demo.)

Calculation Point 1 #(P_1)#

Let #x_1=2#

#y_1=4(2)-1 = 7" " ->" "P_1" "->(x_1,y_1)=(2,7)#

Calculation Point 2 #(P_2)#

Let #x_2=-2#

#y_2=4(-2)-1=-9" "->P_2" "->(x_2,y_2)=(-2,-9)#

Tony B

#color(red)("Notice that point "P_2" is the left most one")#

You always read left to right on the x-axis. Sometimes the reverse order is given in questions setting 'a trap'.

ALWAYS READ LEFT TO RIGHT ON THE X-AXIS FOR WHEN Y IS THE ANSWER
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#color(blue)("Critical point")#

You either need a given point or the equation.

Given equation:#" "y=4x-1#

The x-axis crosses the y-axis at #x=0#
The y-axis crosses the x-axis at #y=0#

Set #x=0" : " y=4x-1" "->" "y=4(0)-1 " "->" "y=-1

So we now have the point: #(x,y)->(0,-1)#

Set #y=0" : "y=4x-1" "->" "0=4x-1 " "->" "x=1/4#

So we now have a second point:#(x,y)->(1/4,0)#