要想提高学生用换元法解方程的能力,应当抓住以下三个问题。用字母表示代数式的能力是用换元法解方程的基础。为了提高学生用字母表示代数式的能力,可以进行这样的训练:将方程中的未知数x换成单项式、多项式、分式或根式。如将7x~2-19x+10=0中的x换成y~2,方程变为7y~4-19y~2+10=0;将x换成y~2-4y+6,方程变为7(y~2-4y+6)~2-19(y~2-4y+6) In order to improve students’ ability to use equations to solve equations, we should seize the following three issues. The ability to use algebraic expressions in letters is the basis for solving equations using the substitution method. In order to improve the ability of students to represent algebraic expressions in letters, such training can be performed by replacing the unknown x in the equation with a monomial, a polynomial, a fraction, or a root. If you replace x in 7x~2-19x+10=0 with y~2, the equation becomes 7y~4-19y~2+10=0; replace x with y~2-4y+6 and the equation becomes 7(y~2-4y+6)~2-19(y~2-4y+6)