A cell phone plan costs ​$30.70 per month for 400 minutes of talk time. It costs an additional ​$0.06 per minute for each minute over 400 minutes. To get​ e-mail access, it costs ​%30 of the price for 400 minutes of talk time. Your​ bill, which includes​ e-mail, is the same each month for 9 months. The total cost for all 9 months is ​$402.39. Write and solve an equation to find the number of minutes of talk time you use each month. Let m represent the number of minutes over minutes each month. Which equation represents the given​ situation?

9m+9*0.3*30.7=402.39

9m+82.89=402.39

9m=319.5

m=35.5minutes/month

9m+9*0.3*30.7=402.39

9m+82.89=402.39

9m=319.5

m=35.5minutes/month

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step-by-step explanation:

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.