Which Plan should Smith buy?
By: Romanch Shah
The situation(cost/extra minute)
y represents the number of minutes
x represents the cost
The data (table of values)
The equations in slope y-intercept form
rate of change:0.6x first difference(6/10)
Cost for Telus(CAD):
rate of change:0.5 first difference (5/10)
The standard form
100(0.6x-y+30.75)=100(0) Multiply by 100 to get rid of the decimals and
60x-100y+3075=0 subtracted y from both sides.
standard form: 60x-100y+3075=0 or 60x-100y=-3075
10(0.5x-y+35)=10(0) Subtracted y from both sides and multiplied by 10 to get rid of the
standard form: 5x-10y+350=0 or 5x-10y=-350
P.O.I.:(42.5,56.25) At 42.5 minutes the cost for both companies is $56.25.
Using equations to solve the P.O.I.
0.6x-0.5x=35-30.75 Rearranging to group like terms
0.1x=4.25 Isolating x
Plug x into any equation, because at this point both points have the same x and y value.
Significance of the linear system
Bell is better when he uses less than 192.5 minutes per month (150 minutes+42.5 minutes), while Telus is better when he goes over than 192.5 minutes per month.