0.80199=t-t2的解

可以将方程重写为 $t^2-t+0.80199=0$ 的标准形式，然后使用求根公式求解：

$$t=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$

将 $a=1, b=-1, c=0.80199$ 带入上式，得到：

$$t=\frac{1\pm\sqrt{1-4\times1\times0.80199}}{2\times1}$$

化简后得到：

$$t_1=0.8948, t_2=0.1052$$

因此方程的解为 $t=0.8948$ 或 $t=0.1052$。

相关问题

检查并修改以下代码，使其运行正确。#include<iostream> using namespace std; class Time{ public: Time(int a,int b,int c){ hour=a; minute=b; second=c; } Time():hour(0),minute(0),second(0){ } Time Drop(Time&t){ Time q; q.hour=hour-t.hour; q.minute=minute-t.minute; q.second=second-t.second; if(q.second<0){ q.minute--; q.second+=60; } if(q.minute<0){ q.hour--; q.minute+=60; } } void disp(){ cout<<hour<<":"<<minute<<"'"<<second<<"""<<endl; } protected: int hour; int minute; int second; }; int main() { int h1,m1,s1,h2,m2,s2; cin>>h1>>m1>>s1>>h2>>m2>>s2; Time t1(h1,m1,s1), t2(h2,m2,s2), t; t=t1.Drop(t2); t.disp(); // t--; t=t.Drop(t); t.disp(); //(--t)--; t=t.Drop(t); t.disp(); //(t--).disp(); t.Drop(t).disp(); t.disp(); return 0; }

以下是代码的修改：

#include<iostream>
using namespace std;

class Time{
public:
    Time(int a,int b,int c){
        hour=a;
        minute=b;
        second=c;
    }
    Time():hour(0),minute(0),second(0){ }
    
    Time Drop(Time&t){
        Time q;
        q.hour=hour-t.hour;
        q.minute=minute-t.minute;
        q.second=second-t.second;
        if(q.second<0){
            q.minute--;
            q.second+=60;
        }
        if(q.minute<0){
            q.hour--;
            q.minute+=60;
        }
        return q; // 添加 return 语句
    }
    
    void disp(){
        cout<<hour<<":"<<minute<<"'"<<second<<"''"<<endl; // 修改输出格式
    }
    
    // 重载运算符
    Time operator--(){ 
        second--;
        if(second<0){
            minute--;
            second+=60;
        }
        if(minute<0){
            hour--;
            minute+=60;
        }
        return *this;
    }
    
    Time operator--(int){
        Time temp=*this;
        --(*this);
        return temp;
    }
    
protected:
    int hour;
    int minute;
    int second;
};

int main() {
    int h1,m1,s1,h2,m2,s2;
    cin>>h1>>m1>>s1>>h2>>m2>>s2;
    Time t1(h1,m1,s1), t2(h2,m2,s2), t;
    t=t1.Drop(t2);
    t.disp();
    
    // t--
    --t; // 先对 t 执行操作
    t.disp();
    
    // (--t)--
    (--t)--; // 先对 t 执行操作，再对操作后的 t 执行操作
    t.disp();
    
    // (t--).disp()
    (t--).disp(); // 先输出 t，再对 t 执行操作
    t.disp();
    
    // t.Drop(t).disp()
    t.Drop(t).disp(); // 直接输出 t.Drop(t) 的结果
    t.disp();
    return 0;
}

主要修改如下：

1. 在 `Time Drop(Time&t)` 函数中添加了 `return` 语句，修复了编译错误。
2. 修改了 `disp()` 函数的输出格式。
3. 重载了 `--` 前置和后置运算符，使其能够对时间进行自减操作（注意修改后置运算符返回值）。
4. 在 `main()` 函数中使用了重载的运算符，以便进行时间的自减和输出操作。

用MySQL8.0写代码，表stock_k_data AS T1 中字段有 ID,open, high, low, close,price,status用游标形式循环逐行计算， T1.字段名表示当前行，T2.字段名表示上一行， t1.ID= 2，循环到最后一行 ， IF t2.status = "买入" AND t1.low<T2.price*0.95,THEN SET t1.status="卖出", t1.price=T2.price*0.95 IF t2.status = "买入" ,THEN t1.status="持有",t1.price=GREATEST(T2.price,T1.high) ELSEIF t2.status= "持有" AND t1.low<GREATEST(T2.price,T1.high)*0.95 ,THEN t1.status="卖出",t1.price=GREATEST(T2.price,T1.high)*0.95 ELSEIF t2.status= "持有" ,THEN t1.status="持有", t1.price=GREATEST(T2.price,T1.high) ELSEIF t2.status = "卖出" AND t1.high>T2.price*1.05,THEN t1.status="买入", t1.price=T2.price*1.05 ELSEIF t2.status = "卖出" ,THEN t1.status="空仓", t1.price=LEAST(T2.price,low) ELSEIF t2.status = "空仓" AND t1.high>LEAST(T2.price,low)*1.05,THEN t1.status="买入", t1.price=LEAST(T2.price,low)*1.05 ELSEIF t2.status = "卖出" ,THEN t1.status="空仓", t1.price=LEAST(T2.price,low) ENDIF

好的，下面是用MySQL8.0实现上述功能的代码：

DECLARE done INT DEFAULT FALSE;
DECLARE cur_id INT;
DECLARE cur_open FLOAT;
DECLARE cur_high FLOAT;
DECLARE cur_low FLOAT;
DECLARE cur_close FLOAT;
DECLARE cur_price FLOAT;
DECLARE cur_status VARCHAR(10);
DECLARE prev_id INT;
DECLARE prev_open FLOAT;
DECLARE prev_high FLOAT;
DECLARE prev_low FLOAT;
DECLARE prev_close FLOAT;
DECLARE prev_price FLOAT;
DECLARE prev_status VARCHAR(10);

DECLARE cur CURSOR FOR SELECT ID, open, high, low, close, price, status FROM stock_k_data WHERE ID >= 2 ORDER BY ID ASC;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

OPEN cur;

FETCH cur INTO cur_id, cur_open, cur_high, cur_low, cur_close, cur_price, cur_status;

WHILE NOT done DO
    IF prev_status = "买入" AND cur_low < prev_price * 0.95 THEN
        SET cur_status = "卖出", cur_price = prev_price * 0.95;
    ELSEIF prev_status = "买入" THEN
        SET cur_status = "持有", cur_price = GREATEST(prev_price, cur_high);
    ELSEIF prev_status = "持有" AND cur_low < GREATEST(prev_price, cur_high) * 0.95 THEN
        SET cur_status = "卖出", cur_price = GREATEST(prev_price, cur_high) * 0.95;
    ELSEIF prev_status = "持有" THEN
        SET cur_status = "持有", cur_price = GREATEST(prev_price, cur_high);
    ELSEIF prev_status = "卖出" AND cur_high > prev_price * 1.05 THEN
        SET cur_status = "买入", cur_price = prev_price * 1.05;
    ELSEIF prev_status = "卖出" THEN
        SET cur_status = "空仓", cur_price = LEAST(prev_price, cur_low);
    ELSEIF prev_status = "空仓" AND cur_high > LEAST(prev_price, cur_low) * 1.05 THEN
        SET cur_status = "买入", cur_price = LEAST(prev_price, cur_low) * 1.05;
    ELSEIF prev_status = "空仓" THEN
        SET cur_status = "空仓", cur_price = LEAST(prev_price, cur_low);
    END IF;

    UPDATE stock_k_data SET status = cur_status, price = cur_price WHERE ID = cur_id;

    SET prev_id = cur_id, prev_open = cur_open, prev_high = cur_high, prev_low = cur_low, prev_close = cur_close, prev_price = cur_price, prev_status = cur_status;

    FETCH cur INTO cur_id, cur_open, cur_high, cur_low, cur_close, cur_price, cur_status;
END WHILE;

CLOSE cur;

该代码通过游标形式循环逐行计算表stock_k_data的数据，并按照给定的条件更新状态和价格。其中，使用了IF-ELSEIF-ELSE语句对不同的状态进行判断和处理。在每次更新完当前行的数据后，将当前行的数据赋值给prev_XXX变量，作为下一次循环时的上一行数据。最后，关闭游标。