? The plus sign is a first-order operation, which is a mathematical symbol used to represent positive numbers or addition. The negative sign is also the first-level operation, which is an operation symbol used to represent negative numbers or subtraction.

? Five hundred years ago, there was a German mathematician named Weidemann. He added a vertical line to the horizontal line and it became "+". He used this symbol to indicate increase. He removed a vertical line from the plus sign and turned it into "-",which means to reduce. Two brothers were born. However, "+"and "-"are officially recognized as symbols of addition and subtraction, starting from the Dutch mathematician Hojk in 154 1 year until now. Therefore, addition and subtraction is one of the two earliest mathematical operations that human beings have mastered.

? Imagine that it would be very troublesome if there were no plus and minus signs for teachers to teach. One plus one cannot be expressed, and one plus one can only be expressed with a stick. If it costs more than 10 thousand, the teacher will find some sticks! So the plus sign and the minus sign are really an indispensable part of life!