If f (x) is defined at point x0, what is the condition (sufficient, necessary or sufficient) for the existence of limit f (x), and vice versa?

Because the existence limit must be continuous, there must be a definition, but there is a definition does not necessarily have a limit, so it is a necessary and insufficient condition

Three conditions must be satisfied for function f (x) to be continuous at point x0. 1: F (x) is defined at point x0, but there is no limit of X tending to x0. 2: limx tends to be continuous

1, the function has definition 2 at x0, there are both left limit and right limit at x0, and the left limit is equal to the right limit 3, and the limit value is equal to the function value

Try to explain that the function f (x) has a definition at x = x0, a limit at x0 and the three probabilities of continuity at x0

If there is a definition, the function value is not equal to the limit value, it is a breakpoint. If there is a definition, the function value is equal to the limit value, it is a continuous point!

How to understand the definition of function limit?
Please help me to introduce the meaning of the two limits. What I don't understand is what a is

What you give is the concept of function limit when the independent variable tends to be positive infinity. This concept should be distinguished from the definition of function limit when the independent variable tends to be a little bit, but in fact, there is no difference in essence. Limit is a property of infinite proximity in the process of change. It is understood that function value and limit value are "arbitrarily small"

What's the square of 5? What's the rule of 15? 25? 35? 45? 55? 65? 75? 85? 95?

5 square = 25, 15 square = 225 rule: for example, 15:1 * 2 = 2, so it is 225, 25:2 * 3 = 6, so it is 625

The school has purchased a number of computers. If each computer is installed with 40, there are still 15 missing. If each computer classroom is installed with 35, there are still 20 more
How many computers has the school purchased? How many computer classrooms does the school have? Please design a plan for the school, which is to install all the computers purchased

The school has x computers and Y computer classrooms
40×y=x+15；35×y=x-20
The solution is: x = 265, y = 7
So there are seven computer classrooms and 265 computers

As shown in the figure is the schematic diagram of a photoelectric counter, where R1 is a resistance made of a semiconductor material, and its value will decrease with the increase of light intensity. R2 is the constant value resistance. The workpiece moves with the conveyor belt, so that the light of the light source irradiates R1 intermittently. The signal processing system between a and B counts once every high voltage is obtained
A. When the light irradiates R1, the voltage at both ends of R1 decreases; the signal processing system counts B. when the light irradiates R1, the voltage at both ends of R1 increases; the signal processing system counts C. when the workpiece blocks the light, the voltage at both ends of R1 decreases; the signal processing system counts D. when the workpiece blocks the light, the voltage at both ends of R1 increases; the signal processing system counts C

It is known from the title that when the light irradiates R1, the resistance value of R1 decreases, the total R decreases, ∵ I = ur, the power supply voltage remains unchanged, the current in the circuit increases, ∵ R2 is the constant resistance, U2 = IR2, ∵ R2 both ends voltage increases, the signal processing system obtains high voltage and counts, ∵ the total voltage of the series circuit is equal to the sum of the partial voltages, ∵ R1 both ends

LIBRARY IEEE;
USE IEEE.STD_ LOGIC_ 1164.ALL;
ENTITY test IS
PORT(
F:IN STD_ LOGIC;
CLK:IN STD_ LOGIC;
CARRY :IN STD_ LOGIC;
RIN:IN STD_ LOGIC_ VECTOR(3 DOWNTO 0);
OUT_ LOW:OUT STD_ LOGIC_ VECTOR(3 DOWNTO 0);
OUT_ HIGH:OUT STD_ LOGIC_ VECTOR(3 DOWNTO 0));
END test;
ARCHITECTURE RTL OF test IS
SIGNAL F_ IN:STD_ LOGIC_ VECTOR(1 DOWNTO 0);
BEGIN
PROCESS(CLK,F,CARRY)
BEGIN
F_ IN

The signal assignment symbol is“

Error (10500):VHDL syntax error at bijiao.vhd (26) near text "PROCESS"; expecting a sequential stat
LIBRARY IEEE;
USE IEEE.STD_ LOGIC_ 1164.ALL;
USE IEEE.STD_ LOGIC_ ARITH.ALL ;
USE IEEE.STD_ LOGIC_ UNSIGNED.ALL ;
ENTITY bijiao IS
PORT(A,B:IN BIT_ VECTOR(3 DOWNTO 0);
F1,F2,F3:OUT BIT);
END bijiao;
ARCHITECTURE behave OF bijiao IS
BEGIN
PROCESS(A,B)
BEGIN
IF(A>B) THEN
F1

The problem is this:
You use else if instead of elsif in the second branch. That is to say, there are two if statements in this statement, and your last end if is only for the nearest if. Therefore, it is recommended that you change the second branch to elsif:)

How to calculate the surface area of a cylinder? The diameter of the upper bottom is 0.25m, the diameter of the lower bottom is 0.3m, and the height of the cylinder is 6.8m. How to calculate the surface area?

r:0.25÷2＝0.125 2×3.14×0.125×(6+0.125)
＝6.28×0.125×6.125
＝0.785×6.125
＝4.0808125(m)

If f (x) is defined at point x0, what is the condition (sufficient, necessary or sufficient) for the existence of limit f (x), and vice versa?