When is a function non differentiable

For a function of one variable, differentiability and differentiability are equivalent. For a function of two variables, if it is differentiable and the derivative is continuous at this point, then it is differentiable!

On the problem of differential function
Limf (x) when x → 0, the function exists. When x = 0, the function does not exist. List several possible functions of F (x) (except the answer of X & sup2 / x). On the contrary, limf (x) when x → 0, the function does not exist. When x = 0, the function exists. List several possible functions of F (x)
I haven't touched my math book for 2 years. Today, I asked a question, but I couldn't answer it

The first one is like f (x) = SiNx / X and so on. The second one can use piecewise function, such as f (x) = 1 (x > 0) f (x) = 2 (x = 0) f (x) = 3 (x)

The problem of function differentiation
If there is a linear function y = KX + B, then y '= K. according to the formula, because there is △ y = f' (x) △ x + α △ x, then there should be △ y = k △ x + α △ X. however, it can be deduced that △ y = f (x + △ x) - f (x) = k △ X. K △ x = k △ x + α △ X

Let △ x = X1 - x0, then △ y = f (x1) - f (x0) = k * (x1-x0) = k * △ X
Consider the case where △ x tends to zero as dy = k * DX
Obviously, K △ x = k △ x + α △ x holds only when α = = 0

Given that Z ∈ C, and | z-2-2i | = 1, I is an imaginary unit, then the minimum value of | Z + 2-2i | is ()
A. 2B. 3C. 4D. 5

Let z = a + bi (a, B ∈ R), the points satisfying | z-2-2i | = 1 are all on the circle with C1 (2, 2) as the center and 1 as the radius, so the minimum value of | Z + 2-2i | is the difference between C1 and C2, that is, 3

There are four new fruits in the fruit shop. The weight of apple is one half of that of the other three fruits, the weight of pear is one third of that of the other three fruits, and the weight of banana is one third
One fourth of the weight of the other three kinds of fruit, pineapple is 299kg, how many kg of fruit are there in the fruit shop?

There are four kinds of new fruits in the fruit shop. The weight of apple is 1 / 2 of that of the other three kinds of fruit. The weight of pear is 1 / 3 of that of the other three kinds of fruit. The weight of banana is 1 / 4 of that of the other three kinds of fruit. The weight of pineapple is 299kg. How many kg of fruit have the fruit shop brought together?
In this way, we can find out that Apple accounts for 1 / 3 of the total fruit; similarly, pear accounts for 1 / 4 of the total fruit and banana accounts for 1 / 5 of the total fruit
299 ÷ (1-1 / 2-1 / 3-1 / 4-1 / 5) = 1380kg
A: the fruit shop has 1380 kilograms of fruit

How to solve these three inequalities,

x²-2x-8≤0 -2 ≤x ≤ 4
x²-9≤0 -3 ≤x ≤ 3
X & # 178; > 2 x ＞ 2 or X ＜ - √ 2

If the direction vector of line L is a = (1,0,2) and the normal vector of plane α is n (- 2,0, - 4), then

l⊥α.

When you go out for an outing, there are 45 people in each car, but 20 people do not. If there are 55 people in each car, there are 30 seats left. How many people are there,

There are x vehicles in total,
If there are 45 people sitting in each car, then if there are 20 people not sitting, the number of people will be 45x + 20
If there are 55 people in each car, there are 30 seats left,
55X-30=45X+20
10X=50
X=5
45X+20
=45*5+20
=225+20
=245
There are five cars and 245 people

Given the eigenvalues 2, - 1,3 of the third-order matrix A, then | a ^ 3-5a|=

The eigenvalues of matrix A ^ 3-5a are - 2,4,12
So | a ^ 3-5a | = - 2 × 4 × 12 = - 96

Why is the normal vector of a plane equal to the product of two nonparallel vectors?
Can you explain it more clearly?

1. The normal vector of a plane is perpendicular to the plane. 2. The vector product of parallel vectors is equal to zero. 3. The vector product of two nonparallel vectors in a plane is perpendicular to the plane

When is a function non differentiable