According to his experience, a retailer estimated that (3000-100x) toy dinosaurs could be sold if they were sold at the price of X yuan per dinosaur. It is known that the cost of toy dinosaurs is 20 yuan 1. Write the formula of Y represented by X 2. Judge how many yuan each toy dinosaur sells, y is the biggest

According to his experience, a retailer estimated that (3000-100x) toy dinosaurs could be sold if they were sold at the price of X yuan per dinosaur. It is known that the cost of toy dinosaurs is 20 yuan 1. Write the formula of Y represented by X 2. Judge how many yuan each toy dinosaur sells, y is the biggest

Let y be profit (I'm sure you've knocked out something, I preliminarily estimate y as profit) (1) y = (3000-100x) * (x-20) and 3000-100x > 0, x-20 > 0, then y = - 100x ＾ 2 + 5000x-60000 and 20 < x < 30 (2) from (1), we can know that - B / 2A = - 5000 / (2 * - 100) =

Quadratic function in junior high school mathematics
If the quadratic function equation of one variable about X - x.x + (2k + 1) x + 2-k.k = 0, then the value range of K is————

From - x ^ 2 + (2k + 1) x + 2-k ^ 2 = 0, we can see that the image of quadratic function must have focus with X axis
So △ = B ^ 2-4ac = (2k + 1) ^ 2-4 * (- 1) (2-k ^ 2) ≥ 0
So 4K ^ 2 + 4K + 1 + 8-4k ^ 2 ≥ 0
4k≥-9
k≥-9/4
*Note "^ 2" means square
I don't know if you've ever learned △ = B ^ 2-4ac
But this is the easiest way to solve the problem~

If the parabola y = x ^ 2 intersects with the straight line y = x + m, then the value range of M

x^2=x+m
x^2-x-m=0
(-1)^2-4*1*(-m)>=0
m>=-1/4