Brad bought a shirt at a 20% discount and with sales tax of 5%. How can the expression 1.05(x - 0.2x) be rewritten to show what percentage of the original price he paid?a) 0.84x b) 0.85x
c) 0.21x
d) 0.8x

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