论文部分内容阅读
多元条件求值题是一种重要题型,常见于初中数学竞赛,它思路新颖、解法灵活、技巧性强,解这类题同学们常感困难,现介绍几种思路.方法、技巧,供同学们参考.一、拆项,凑求值式,整体求值例1已知方程组{3x+7y+z=3,4x+10y+z=4,则x+y+z的值是.解原方程组拆项组合得{(x+y+z)+2(x+3y)=3,(1)(x+y+z)+3(x+3y)=4.(2)(1)×3-(2)×2,得x+y+z=1.点评拆项考虑到求值式是关键.二、添项、去项,凑已知条件,整体求值.
Multivariate conditional evaluation is an important problem, common in junior high school mathematics competition, which novel ideas, flexible solution, strong skill, solution of these questions students often feel difficult, is to introduce several ideas. Methods, techniques for Students refer to the following: 1. Disassembled Item, Coalesce Value, Overall Evaluation Example 1 The known system of equations {3x + 7y + z = 3,4x + 10y + z = 4, the value of x + y + z is. (2) (3) (3) (4) (2) (2) () () () 1) × 3- (2) × 2, so that x + y + z = 1. Comment disassembly considering the evaluation formula is the key. Second, add items to items, get together known conditions, the overall value.