Teresa eats in a resturaunt that charges 6% sales tax on the cost of a meal. teresa decides to leave a tip that equals 18% of the cost of her meal.
which expression represents the total amount teresa will pay for a meal, where x is the cost of her meal before the tax and tip?
a. x+x(0.06)+x(0.18)
b. x+(x+0.06)+(x+0.18)
c. x+(x-0.06)+(x-0.18)
d. x+x(1+0.06)+x(1+0.18)

the first one

step-by-step explanation:

just id the test.

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204