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Mathematical statistics：
Enter the data to be counted, separated by commas (","), and click Next to get the statistics results.
Statistical items: total data, sum, average, variance and standard deviation.
Note: Statistical data can only be numbers, which cannot be algebraic expressions or mathematical functions (including trigonometric functions).
Enter the data to be counted, separated by commas (","), and click Next to get the statistics results.
Statistical items: total data, sum, average, variance and standard deviation.
Note: Statistical data can only be numbers, which cannot be algebraic expressions or mathematical functions (including trigonometric functions).
Current location：Mathematical operation > History of Mathematical Statistics > Answer
Overview: 1 questions will be solved this time.Among them
☆1 equations
[ 1/1 Equation]
Work: Find the solution of equation (4+0.4n)*(20-n) = 0 .
Question type: Equation
Solution:Original question:
| ( | 4 | + | 2 5 | n | ) | ( | 20 | − | n | ) | = | 0 |
| Left side of the equation = | 4 | ( | 20 | − | n | ) | + | 2 5 | n | ( | 20 | − | n | ) |
| = | 4 | × | 20 | − | 4 | n | + | 2 5 | n | ( | 20 | − | n | ) |
| = | 80 | − | 4 | n | + | 2 5 | n | ( | 20 | − | n | ) |
| = | 80 | − | 4 | n | + | 2 5 | n | × | 20 | − | 2 5 | n | n |
| = | 80 | − | 4 | n | + | 8 | n | − | 2 5 | n | n |
| = | 80 | + | 4 | n | − | 2 5 | n | n |
| 80 | + | 4 | n | − | 2 5 | n | n | = | 0 |
After the equation is converted into a general formula, it is converted into:
( n + 10 )( n - 20 )=0
From
n + 10 = 0
n - 20 = 0
it is concluded that:：
n1=-10
n2=20
There are 2 solution(s).
解一元二次方程的详细方法请参阅：《一元二次方程的解法》