在等比性质的证明中,常常先根据题设中一连串相等的比设立比值k,通过k建立分子和分母的关系式,然后适当变形而完成证明.这种巧设比值的方法在解题中十分有用.现举几例说明.一、求代数式的值例1若x3=y4=z5,则2x+y-zx=.解:设x3=y4=z5=k,则x=3k,y=4k,z=5k,∴原式=6k+4k-5k3k=53.二 In the proof of equal ratio property, the ratio k is often set according to a series of equal ratios in the question set. The relationship between the numerator and the denominator is established by k, and then the appropriate derivation is used to complete the proof. This method of skillfully setting the ratio is used to solve the problem. Very useful. Now give a few examples. First, the value of algebraic expressions Example 1 If x3 = y4 = z5, then 2x + y-zx =. Solution: Let x3 = y4 = z5 = k, then x = 3k, y = 4k, z=5k, ∴ original type=6k+4k-5k3k=53. two