Use fzero in MATLAB to solve the root of equation x ^ 2. * exp (- x ^ 2) = 0.2 in interval [- 2,2]?

Use fzero in MATLAB to solve the root of equation x ^ 2. * exp (- x ^ 2) = 0.2 in interval [- 2,2]?

fzero(@(x)x.^2.*exp(-x.^2)-0.2,0)

In Matlab: define the function myfun: Y (1,2) = [200 * sin (x) / x, x ^ 2], and draw the graph of the function in the interval of x = [- 20,20]

function    Y=myfun(x)
Y(:,1)=200*sin(x(:))./x(:);
Y(:,2)=x(:).^2;
Then enter in the command window
fplot('myfun',[-20    20])

Matlab finds the function f = (1 + x ^ 2) / (1 + x ^ 4) in the interval 0

First, the exact solution can be obtained by analytical method. Find the derivative of F to x, make it equal to 0, and find x = √ (√ 2-1) or - 1. Therefore, the maximum value is (1 + √ 2) / 2. Enter (1 + sqrt (2)) / 2 in MATLAB to get 1.2071. If I have to solve it, my idea is: A. first draw and observe the function curve, such as the following command

Y = ln (1 + x square), find the extreme value of the function and the inflection point of the curve

Find the first derivative
y'=2x/(1+x ²)
Let y '= 0 get x = 0
When x = 0, the function has a minimum value Y (min) = ln (1 + 0 ²)= ln1=0
Find the second derivative
y''=[2(1+x ²)- 2x(2x)]/(1+x ²)²= (2-2x ²)/ (1+x ²)²
Let y '' = 0, 2-2x ²= 0,x ²= 1,x=±1
There are two inflection points, (1, LN2), (- 1, LN2)

Find the extreme value of the monotone interval of the function y = ln (x square + 1) and the concave interval and inflection point of the function curve, and find a clear picture that can be solved with pen and paper Because I'm afraid I can't understand the symbols or use Chinese instead

The detailed process of solving this problem is as follows:

Find the source: the function f (x) whose definition domain is interval [a, b] is known, and its image is a continuous curve, which satisfies the following requirements This question is the 10th in the math monthly exam of that school in Zhejiang Province

It is known that the function f (x) whose definition domain is interval [a, b] is a continuous curve and satisfies the following conditions:
1. The range of F (x) is g, and G ∈ [a, b]
2. For any different x, y ∈ [a, b], there is | f (x) - f (y)|