quadratic equation with one unknown

例句：

1. 1.The quadratic equation x^2 - 4x + 4 = 0 has two solutions.
   这个二次方程 x^2 - 4x + 4 = 0 有两个解。
2. 2. Thequadratic equation can be solved using the quadratic formula.
   这个二次方程可以用二次公式来解。
3. 3. The quadratic equation is a type of polynomial equation that involves the square of a variable.
   二次方程是一种涉及变量平方的多项式方程类型。