Gillian purchased 25 books at the library book sale. each hardcover book cost $1.50, and each paperback book cost $0.50. gillian spent a total of $26.50. the book costs can be represented by the system of equations below.

h + p = 25.
1.50h + 0.50p = 26.50

how many paperback books did gillian buy?

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