总述:本次共解1题。其中
☆方程1题
〖 1/1方程〗
作业:求方程 20×1000(1-3/8a%)+30(1-a%)×(1500-1000)(1+2a%) = 20×1000+30×(1500-1000) 的解.
题型:方程
解:原方程:| | 20 | × | 1000 | ( | 1 | − | 3 | ÷ | 8 | × | a% | ) | + | 30 | ( | 1 | − | a% | ) | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) | = | 20 | × | 1000 | + | 30 | ( | 1500 | − | 1000 | ) |
| 方程左边 = | 20000 | ( | 1 | − | 3 | ÷ | 8 | × | a% | ) | + | 30 | ( | 1 | − | a% | ) | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
方程化为:
| | 20000 | ( | 1 | − | 3 | ÷ | 8 | × | a% | ) | + | 30 | ( | 1 | − | a% | ) | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) | = | 20 | × | 1000 | + | 30 | ( | 1500 | − | 1000 | ) |
去掉方程左边的括号:
| 方程左边 = | 20000 | × | 1 | − | 20000 | × | 3 | ÷ | 8 | × | a% | + | 30 | ( | 1 | − | a% | ) | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 20000 | − | 75 | a | + | 30 | ( | 1 | − | a% | ) | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 20000 | − | 75 | a | + | 30 | × | 1 | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) | − | 30 | × | a% | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 20000 | − | 75 | a | + | 30 | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 20000 | − | 75 | a | + | 30 | × | 1500 | ( | 1 | + | 2 | × | a% | ) | − | 30 | × | 1000 | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a | ( | 1500 | − | 1000 | ) |
| = | 20000 | − | 75 | a | + | 45000 | ( | 1 | + | 2 | × | a% | ) | − | 30000 | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 20000 | − | 75 | a | + | 45000 | × | 1 | + | 45000 | × | 2 | × | a% | − | 30000 | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a |
| = | 20000 | − | 75 | a | + | 45000 | + | 900 | a | − | 30000 | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 65000 | + | 825 | a | − | 30000 | ( | 1 | + | 2 | × | a% | ) | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 65000 | + | 825 | a | − | 30000 | × | 1 | − | 30000 | × | 2 | × | a% | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 65000 | + | 825 | a | − | 30000 | − | 600 | a | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | + | 225 | a | − | 3 10 | a | ( | 1500 | − | 1000 | ) | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | + | 225 | a | − | 3 10 | a | × | 1500 | ( | 1 | + | 2 | × | a% | ) | + | 3 10 | a | × | 1000 | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | + | 225 | a | − | 450 | a | ( | 1 | + | 2 | × | a% | ) | + | 300 | a | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | + | 225 | a | − | 450 | a | × | 1 | − | 450 | a | × | 2 | × | a% | + | 300 | a |
| = | 35000 | + | 225 | a | − | 450 | a | − | 9 | a | a | + | 300 | a | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | − | 225 | a | − | 9 | a | a | + | 300 | a | ( | 1 | + | 2 | × | a% | ) |
| = | 35000 | − | 225 | a | − | 9 | a | a | + | 300 | a | × | 1 | + | 300 | a | × | 2 |
| = | 35000 | − | 225 | a | − | 9 | a | a | + | 300 | a | + | 6 | a | a |
| = | 35000 | + | 75 | a | − | 9 | a | a | + | 6 | a | a |
方程化为:
| | 35000 | + | 75 | a | − | 9 | a | a | + | 6 | a | a | = | 20 | × | 1000 | + | 30 | ( | 1500 | − | 1000 | ) |
| 方程右边 = | 20000 | + | 30 | ( | 1500 | − | 1000 | ) |
方程化为:
| | 35000 | + | 75 | a | − | 9 | a | a | + | 6 | a | a | = | 20000 | + | 30 | ( | 1500 | − | 1000 | ) |
方程化为一般式后,用因式分解法化为:
( a +0 )( a - 25 )=0
由
a + 0 = 0
a - 25 = 0
得:
a1=0
a2=25
有 2个解。
解一元二次方程的详细方法请参阅:《一元二次方程的解法》
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