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习题再现(九年级数学人教版教材上册第22页第6题)当x=5~(1/2)-1时,求代数式x~2+5x-6的值.分析:解这道题的方法比较简单,只需将x的值代入化简即可,但运算时较易出错.解:将x=5~(1/2)-1代入x~2+5x-6可知,原式=(5~(1/2)-1)~2+5×(5~(1/2)-1)-6=5-2(5~(1/2)+1+5(5~(1/2)-5-6=3(5~(1/2))-5.解本题需运用二次根式的乘法运算法则及二次根式的加减运算法则.一些同学由于运算能力较差,常出错.同时,一部分同学对本题的解题方法形成思维定式,不考虑题目的特点,凡此类问题不论繁简,都直接代入,从而导致运算烦琐.此类问题在中考试
Exercises recurrence (ninth grade Mathematics PEP Teaching Materials Volume on page 22, No. 6) When x = 5 ~ (1/2) -1, find the algebraic value of x ~ 2 +5 x-6 value. The method is relatively simple, just the value of x into simplified, but the operation is more error-prone. Solution: Substituting x = 5 ~ (1/2) -1 into x ~ 2 + 5x-6 shows that the original = (5-1 / 2) -1 + 2 + 5 × (5-1/2) -1 -6 = 5-2 1/2) -5-6 = 3 (5 ~ (1/2)) - 5. This problem requires the use of quadratic root multiplication and quadratic root addition and subtraction algorithms. Some students due to poor computing power , Often mistakes.At the same time, part of the students on the problem-solving method to form a thinking formula, regardless of the characteristics of the topic, such problems regardless of complexity, are directly into, resulting in computational cumbersome.