【求助】小白自学C++遇到问题

#include <iostream>
#include <cmath>
using namespace std;
int main() {
double a, b, c, o, p, q, i, x, y;
cout <<
"输入a，b，c的值，以求得函数的性质及其图像与坐标轴的交点："
<< endl << "a=";
cin >> a;
cout << "b=";
cin >> b;
cout << "c=";
cin >> c;
cout << "该函数为";
if (a = 0) {
if (c = 0)
cout << "正比例函数，与坐标轴交于原点" << endl;
else {
i = -c / b;
cout << "一次函数，与X轴交点为（" << i <<
"，0），与Y轴交点为（0，" << c << "）" << endl;
}
} else {
y = -b / (2 * a);
cout << "二次函数，与";
if (c = 0) {
if (b = 0)
cout << "坐标轴交于原点" << endl;
else {
x = 2 * y;
cout << "坐标轴交于原点及点（" << x <<
"，0），其对称轴为x=" << y << endl;
}
} else {
o = b * b - 4 * a * c;
cout << "Y轴交于点（0，" << c << ")";
if (o < 0)
cout << endl;
else {
cout << "与X轴交于点（";
if (o = 0)
cout << y << "，0）" << endl;
else {
p = (-b + sqrt(o)) / (2 * a);
q = (-b - sqrt(o)) / (2 * a);

cout << p << "，0）、（" << q << "，0），其对称轴为x=" <<
y << endl;
}
}
}
}
return 0;
}

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初学的话,还是用电脑吧.手机上编程也就玩玩.