Carina bought a spiral notebook that cost x dollars and a binder that cost 2.5 times as much as the notebook . Her total cost was $4 .20. How much did the spiral notebook cost?

go and ask your mom to you

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

75%

step-by-step explanation: