The formula Y=KX is used in the proportional function, and then the known value is brought in to find out what the value of k is. Such as; X=2, Y=4. The analytical expression of this function is: Y=2X. Analysis: As I said, bring the known values of X and Y into the formula Y=KX, 4=2K, write the formula to find the value of K, and then find K=2. Then bring K=2 into the original formula. X and y can not be replaced by numerical values, but directly expressed by letters. In this way, we can find the analytic formula Y=2X of the proportional function. Replace k with the known 2.

Linear function. . The formula is Y=KX+b ... For example, the base camp temperature of a mountaineering team is 5℃. Every time the altitude rises 1 km, the temperature drops by 6℃. When the climber climbs Xkm from the base camp, the temperature at his position is Y℃, and the relationship between Y and X is expressed by analytical formula. . . . . . . . . . . . . Analysis: The topic says that their original temperature is 5℃, so it is concluded that the original temperature+the temperature after climbing Xkm = the temperature of their location. . The formula Y=5+(-6X) is simplified to Y=5-6X. . Or Y=-6X+5. . Be sure to write the last two in the exam. . . The last two are the resolution functions we require.