Show work for the following four questions: 1: x^2 + 4x = -13
2: 3x^2 = 11x + 4
3: 2x^2 + 11x = -7
4: x^2 - 8x - 20 = 0

1/2*qr*rs

step-by-step explanation:

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