2. An equation with an unknown number is an equation.

3. Equation must be an equation; An equation is not necessarily an equation. Equation.

4. Adding or subtracting the same number on both sides of the equation at the same time results in an equation. This is the essence of the equation.

When both sides of an equation are multiplied or divided by the same number that is not equal to 0, the result is still an equation. This is also the nature of the equation.

5. The process of finding the unknown quantity in the equation is called solving the equation.

Common relations in solving equations:

One addend = sum-another addend = minuend-difference = minuend+difference.

One factor = product divisor of another factor = dividend quotient dividend = quotient divisor.

Note: After solving the equation, you should form a good habit of testing.

6. The sum of five consecutive natural numbers (or consecutive odd numbers and consecutive even numbers) is equal to five times the median number. The sum of odd consecutive natural numbers (or even consecutive odd numbers) = intermediate number.

7. The sum of four consecutive natural numbers (or consecutive odd numbers or even numbers) is equal to the sum of the middle two numbers or the first two numbers (Gaussian sum formula).