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笔者在同学们的练习中发现,同学们在解一元二次方程时,容易出现以下几个问题.一、忽略前提,乱套公式例1解方程:x~2+3x=4.错解:因为△=3~2×1×4=-7<0,所以方程无解.点评:用公式法解一元二次方程,必须先把方程化为一般形式ax~2+bx+c=0(a≠0).如果同学们没有理解这一点,胡乱地套用公式,解方程时就会造成错误.正解:方程可化为x~2+3x-4=0.
The author found in the practice of students, students solve the quadratic equation of a dollar, prone to the following problems: First, ignore the premise, random formula 1 solutions equation: x ~ 2 + 3x = 4. wrong solution: because △ = 3 ~ 2 × 1 × 4 = -7 <0, so the equation has no solution. Comment: To solve the unary quadratic equation by the formula, we must first equation into the general form ax ~ 2 + bx + c = 0 ≠ 0). If students do not understand this, random formula, formulate the equation will result in error. Positive solution: The equation can be transformed into x ~ 2 + 3x-4 = 0.