Which of the following is not always true about a rhombus?
a) all sides are congruent.
b) all angles are congruent.
c) it has two pairs of parallel sides.
d) it has two pairs of congruent angles.

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

thats not a system of equations, that is a solution