一元二次方程ax2+bx+c=0(a≠0),当x∈R时,当且仅当△=b2-4ac≥0,判别式法在数学解题中有着广泛应用,但学生往往忽视它成立的三个条件;x∈R;a≠0;实系数;否则将会出现错误,下面分类说明. 条件一 x∈R. 例1 方程sin2x-2asinx+3a=0有解,求a的取值范围. The unitary quadratic equation ax2 + bx + c = 0 (a ≠ 0), when x ∈ R, if and only if △ = b2-4ac ≥ 0, the discriminant method has been widely used in mathematical problem solving, but students often Ignore the three conditions for which it is established; x∈R;a≠0; real coefficient; otherwise, an error will occur. The following classification is explained. Condition one x∈R. Example 1 Equation sin2x-2asinx+3a=0 has solution, find a The range of values.