Let these two numbers be a and b respectively, then a+b = 4; a-b = 4； a=4，b=0 .
Mathematical calculation method:
1, fast addition: the calculation method of fast addition of arbitrary numbers is very simple. Learners only need to memorize a general formula of quick addition-"Standard addition (for decimal digits) minus plus complement, and the previous digit plus one" to completely solve the quick addition method of counting any digits from high to low, such as:
( 1), 67+48 = (6+5) × 10+(7-2) = 1 15, (2) 758+496 = (7+5) × 100.
2. Subtraction Fast Calculation: The calculation of any digit subtraction fast calculation method is also a general formula of subtraction fast calculation-"Standard subtraction (borrowed digits) plus or minus one" can completely solve any digit subtraction fast calculation method from high to low digits, such as:
( 1), 67-48 = (6-5) × 10+(7+2) = 19, (2), 758-496 = (7-5) × 100+(5
3. Fast multiplication: The general formula of Wei's fast multiplication is AB× CD = (a+1)× C×100+B× D+the number of Wei's fast multiplication×10.
Fast calculation of evolution number |=(a-c)×d+(b+d- 10)×c,
Fast calculation of evolution number ‖=(a+b- 10)×c+(d-c)×a,
Quickly calculate the evolution number ⅲ= a×d-' b' (complement )× C. It is unique and unparalleled.