总述:本次共解1题。其中
☆方程1题
〖 1/1方程〗
作业:求方程 (100+5x)(140+3x)(150+2x) = 290(150+2x)(140+3x)-2x(140+3x)(140+3x)-3x(150+2x)(150+2x) 的解.
题型:方程
解:原方程: | ( | 100 | + | 5 | x | ) | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) | = | 290 | ( | 150 | + | 2 | x | ) | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 | x | ( | 150 | + | 2 | x | ) | ( | 150 | + | 2 | x | ) |
去掉方程左边的括号:
方程左边 = | 100 | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 100 | × | 140 | ( | 150 | + | 2 | x | ) | + | 100 | × | 3 | x | ( | 150 | + | 2 | x | ) | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 14000 | ( | 150 | + | 2 | x | ) | + | 300 | x | ( | 150 | + | 2 | x | ) | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 14000 | × | 150 | + | 14000 | × | 2 | x | + | 300 | x | ( | 150 | + | 2 | x | ) | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 2100000 | + | 28000 | x | + | 300 | x | ( | 150 | + | 2 | x | ) | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 2100000 | + | 28000 | x | + | 300 | x | × | 150 | + | 300 | x | × | 2 | x | + | 5 | x |
= | 2100000 | + | 28000 | x | + | 45000 | x | + | 600 | x | x | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 2100000 | + | 73000 | x | + | 600 | x | x | + | 5 | x | ( | 140 | + | 3 | x | ) | ( | 150 | + | 2 | x | ) |
= | 2100000 | + | 73000 | x | + | 600 | x | x | + | 5 | x | × | 140 | ( | 150 | + | 2 | x | ) | + | 5 | x |
= | 2100000 | + | 73000 | x | + | 600 | x | x | + | 700 | x | ( | 150 | + | 2 | x | ) | + | 15 | x | x |
= | 2100000 | + | 73000 | x | + | 600 | x | x | + | 700 | x | × | 150 | + | 700 | x | × | 2 |
= | 2100000 | + | 73000 | x | + | 600 | x | x | + | 105000 | x | + | 1400 | x | x | + | 15 |
= | 2100000 | + | 178000 | x | + | 600 | x | x | + | 1400 | x | x | + | 15 | x | x |
= | 2100000 | + | 178000 | x | + | 600 | x | x | + | 1400 | x | x | + | 15 | x | x |
= | 2100000 | + | 178000 | x | + | 600 | x | x | + | 1400 | x | x | + | 2250 | x | x |
方程化为:
| 2100000 | + | 178000 | x | + | 600 | x | x | + | 1400 | x | x | + | 2250 | x | x | = | 290 | ( | 150 | + | 2 | x | ) | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 | x | ( | 150 | + | 2 | x | ) | ( | 150 | + | 2 | x | ) |
去掉方程右边的括号:
方程右边 = | 290 | × | 150 | ( | 140 | + | 3 | x | ) | + | 290 | × | 2 | x | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 |
= | 43500 | ( | 140 | + | 3 | x | ) | + | 580 | x | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 | x | ( | 150 | + | 2 | x | ) |
= | 43500 | × | 140 | + | 43500 | × | 3 | x | + | 580 | x | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) |
= | 6090000 | + | 130500 | x | + | 580 | x | ( | 140 | + | 3 | x | ) | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 | x |
= | 6090000 | + | 130500 | x | + | 580 | x | × | 140 | + | 580 | x | × | 3 | x | − | 2 | x |
= | 6090000 | + | 130500 | x | + | 81200 | x | + | 1740 | x | x | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) |
= | 6090000 | + | 211700 | x | + | 1740 | x | x | − | 2 | x | ( | 140 | + | 3 | x | ) | ( | 140 | + | 3 | x | ) | − | 3 | x |
= | 6090000 | + | 211700 | x | + | 1740 | x | x | − | 2 | x | × | 140 | ( | 140 | + | 3 | x | ) | − | 2 | x |
= | 6090000 | + | 211700 | x | + | 1740 | x | x | − | 280 | x | ( | 140 | + | 3 | x | ) | − | 6 | x | x |
方程化为一般式后,有公因式:
( 2x + 133 )
由
2x + 133 = 0
得:
不能由因式分解法得出的解:
x2≈-52.412684 ,保留6位小数
x3≈19.079351 ,保留6位小数
有 3个解。
解程的详细方法请参阅:《方程的解法》
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