How much is △ Y / △ x equal to if you know the 1 point (1, - 2) on the image with function f (x) = 2x ^ 2-4 and the adjacent point (1 + △ x, - 2 + △ y)

How much is △ Y / △ x equal to if you know the 1 point (1, - 2) on the image with function f (x) = 2x ^ 2-4 and the adjacent point (1 + △ x, - 2 + △ y)

△ Y / △ x is actually the slope of flying (x) at points (1, - 2). The derivative of F (x) is 4x and the slope at x = 1 is 4, that is
△ Y / △ x = 4, you can look at the definition of slope (that is, the derivative of a point) to help you understand!

The functional relationship between the area y (cm2) of the circle and the radius x (CM) of the circle is _

From the area calculation formula of the circle, y = π x2

Is there a functional relationship between the area and radius of a circle?

Yes, the radius is determined and the area is determined
S=πr ²

Write the definition of circle area function in VB to calculate the area of circle with radius 3,3.5,4,4.5

Function definition name area, parameter r
Function Area(r)
Area = 3.1415926 * r * r
End Function
Call example:
Private Sub Command1_ Click()
Label1.Caption = Area(Val(Text1.Text))
End Sub

Define a circle class, including the data member R (radius), the member function area (), and calculate the area of the circle. Define an object B for testing

class Circle
{
public:
Circle(int nr ){ r = nr; }
Circle(){}
public:
int r;
int Area()
{ return 3.14 * r * r; }
};
class B
{
public:
B()
{
Circle c(10);
int n = c.Area();
}
B(){}
};

For a circle with radius r, if the radius increases by X, the area of the circle increases by S. what is the functional relationship between the area s and X?

S1=pai*r2
S2=pai*(r+x)2
S=S2-S1=pai*[(r+x)2-r2]=pai*[r2-2xr+x2-r2]
=pai*(x2-2xr)=pai*x*(x-2r)
I've written so much on such a question. How sweaty!