David works at the t-shirt shack selling tees. the equation y = 15x – 520 represents the profit that the t-shirt shack makes for each t-shirt sold, where y is the total profit and x is the number of t-shirts sold.
• how many t-shirts does the t-shirt shack need to sell to make a profit of $140?

Step-by-step explanation:

y = 15x - 520...and y represents the total profit

so if he wants to make a total profit of 140, sub in 140 for y and solve for x

140 = 15x - 520

140 + 520 = 15x

660 = 15x

660/15 = x

44 = x <=== they need to sell 44 t-shirts to make a profit of $ 140

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.