What is question 7 how to do it step by step

2020

Step-by-step explanation:

C is defined as the # of new cars sold and t is defined as years after 1998.

If we want to find the year when the # of new cars purchased reached 15,000, we can set C equal to 15000.

15000=20t^2 + 135t + 3050

Subtract both sides by 15000 so you can set the equation equal to zero.

0= 20t^2 + 135t - 11950

Since this is a bit bulk we, more practically, should use the quadratic formula.

((-135) +/- sqrt((135)^2)-4(20)(-11950)))/2(20)

= ((-135) + 987.0284)/40 (We are adding because we assume that we aren't going in the past as the question states "will the number" to implies in the future)

=852.02837/40

=21.3007

Round to 22 years

Since we are finding the year, and the start is 1998 we add 22 to get the answer 2020.

You can plug in that value to get 15700 new cars sold. (This value is not exactly 15000, but unless 2019.3007... is an acceptable answer, I suggest to round to 2020)

$8

step-by-step explanation:

it is pretty much backwards.

you take the 4x2 multiply that, and that is = $8