A store sells hardcover books for $8 and paperback books for $5. You buy 9 books, represented by the equation x + y = 9, where x is the number of hardcover books and y is the number of paperback books. The equation 8x + 5y = 57 represents the total cost. How many of each type of book did you buy?

i believe

step-by-step explanation:

from my conclusion c

no i do not : ( what is it?

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

b. hoped i'm right lol

step-by-step explanation: