# Junior High School Olympiad # Introduction to the Olympic Mathematical Competition or Mathematical Olympiad, referred to as Olympiad. Olympic mathematics embodies the commonality between mathematics and the Olympic spirit: faster, higher and stronger. As an international competition, the International Mathematical Olympiad was put forward by international mathematical education experts, which exceeded the level of compulsory education in various countries and was much more difficult than the college entrance examination. Olympic Mathematics has a certain effect on teenagers' mental exercise, which can exercise their thinking and logic, and it plays a more profound role for students than ordinary mathematics. The following are the knowledge points of Olympiad in the second day of junior high school: addition and subtraction of scores, welcome to read.

1, add and subtract fractions with the same denominator.

The law of addition and subtraction of the same denominator fraction is: addition and subtraction of the same denominator fraction and addition and subtraction of the same denominator numerator. The result of addition and subtraction must be reduced to the simplest fractional or algebraic expression.

Expressed as:

Fractional addition and subtraction with the same denominator

Understanding of the law:

The "addition and subtraction of molecules" in (1) law refers to the addition and subtraction of molecules of each fraction as a whole, that is, each molecule has brackets. When the molecule is monomial, brackets can generally be omitted; When the numerator is a polynomial, especially when doing subtraction, the brackets can't be omitted.

The denominator in the law is a constant, that is, the denominator taken during addition and subtraction is the denominator in the original fraction.

2. Fractional addition and subtraction with different denominators

The law of addition and subtraction of fractions with different denominators is: add and subtract fractions with different denominators, first divide fractions with the same denominator, and then add and subtract. It is expressed as:

Fractional addition and subtraction with different denominators

General steps of adding and subtracting fractions of different denominators:

① General division, that is, changing fractions with different denominators into fractions with the same mother.

Write in the form of "denominator unchanged, numerator addition and subtraction".

(3) Remove the brackets in the molecule and merge the similar items.

(4) Fraction of numerator and denominator, and turn the result into the simplest fractional or algebraic expression.