ios - Swift - 二次方程求解器给出错误的结果？

Question

我是 swift 的新手，我正在尝试制作一个简单的应用程序来求解方程式(线性或二次方程式)。用户必须输入 a、b、c 的值(方程为:ax^2 + bx + c = 0)，如果 a = 0，应用程序求解线性方程，如果 a != 0，应用程序求解二次方程(或告诉它无解)。

问题是.. 线性方程部分工作得很好并且给出了正确的结果，但是该应用程序给出了二次方程的错误结果!例如，如果 a = 4，b = 12，c = 8，结果应该是 x1 = - 1，x2 = -2，但我在应用程序中得到的解决方案是 x1 = -16.0，x2 = -32.0

x1/x2 似乎是对的(0.5)但结果完全错误

这是我写的代码

import UIKit
import Foundation

class ViewController: UIViewController {

@IBOutlet weak var EnterA: UITextField!
@IBOutlet weak var EnterB: UITextField!
@IBOutlet weak var EnterC: UITextField!
@IBOutlet weak var LabelYourEquation: UILabel! // gonna deal with this later
@IBOutlet weak var Button: UIButton!
@IBOutlet weak var LabelX1: UILabel!
@IBOutlet weak var LabelX2: UILabel!


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    Hide()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


var a = Double()
var b = Double()
var c = Double()
var delta = Double()
var x1 = Double()
var x2 = Double()
var linearEquation = Bool()
var quadraticEquation = Bool()

func checkEquation() {
    if a == 0 {
        linearEquation = true
        quadraticEquation = false
    } else if a != 0 {
        quadraticEquation = true
        linearEquation = false
    }
}



func linearEquationResolution() -> Double {
    x1 = -c / b
    LabelX2.hidden = true
    LabelX1.text = "x = \(x1)"
    return x1
}


func Delta() -> Double {
    delta = (b * b) - (4 * a * c)
    return delta
}

func quadraticEquationResolution() {
    if delta >= 0 {
        x1 = ( -b + sqrt(delta)) / 2*a
        x2 = ( -b - sqrt(delta)) / 2*a
        LabelX1.hidden = false
        LabelX2.hidden = false
        LabelX1.text = "x1 = \(x1)"
        LabelX2.text = "x2 = \(x2)"

    } else if delta < 0 {
        LabelX1.text = "The equation has no solution"
        LabelX2.hidden = true

    }
}


func solveIt() {
    if linearEquation == true {
        linearEquationResolution()
    } else if quadraticEquation == true {
        Delta()
        quadraticEquationResolution()
    }
}


func Hide() {
    LabelX2.hidden = true
    LabelX1.hidden = true
}





@IBAction func SolveItAction(sender: AnyObject) {

    a = Double(EnterA.text!)!
    b = Double(EnterB.text!)!
    c = Double(EnterC.text!)!
    checkEquation()
    solveIt()

 }




}

有什么想法吗？我做错了什么？

Answer 1

你错误地乘以 a 而不是除以

( -b + sqrt(delta)) / (2*a)