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標題:
Math hw!! about max &min
發問:
18. Find two numbers whose difference is 44 and whose product is at the minimum. 19. Find two numbers whose sum is 100 and whose product is at the maximum. 更新: 我不明白找了x後怎樣找那兩個數值 我想問19. X為何不是= -50??
最佳解答:
18. Let x be the larger number, y be the product y=x(x-44) =x^2-44x =(x^2-44x+22^2)-22^2 =(x-22)^2-484 So when x=22 and the minimum value is obtained. And the two numbers are 22 and -22. 19. Let x be the smaller number, y be the product. y=x(100-x) =-x^2+100x = -(x^2-100x+2500)+2500 = -(x-50)^2+2500 So when x=50 and the maximum value is obtained. And the two numbers are 50. 2011-11-14 17:57:40 補充： 1. I have let x to be one of the value. By using other info.(such as sum or difference), u canget the another number. 2. u can try to put -50 and the another value as 150 and see if that is maximum.
其他解答:
Math hw!! about max &min
發問:
18. Find two numbers whose difference is 44 and whose product is at the minimum. 19. Find two numbers whose sum is 100 and whose product is at the maximum. 更新: 我不明白找了x後怎樣找那兩個數值 我想問19. X為何不是= -50??
最佳解答:
18. Let x be the larger number, y be the product y=x(x-44) =x^2-44x =(x^2-44x+22^2)-22^2 =(x-22)^2-484 So when x=22 and the minimum value is obtained. And the two numbers are 22 and -22. 19. Let x be the smaller number, y be the product. y=x(100-x) =-x^2+100x = -(x^2-100x+2500)+2500 = -(x-50)^2+2500 So when x=50 and the maximum value is obtained. And the two numbers are 50. 2011-11-14 17:57:40 補充： 1. I have let x to be one of the value. By using other info.(such as sum or difference), u canget the another number. 2. u can try to put -50 and the another value as 150 and see if that is maximum.
其他解答:
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y = a(x-h)2 + k when a >0,the graph open upward , h=minimum when a< 0 , the graph open downward, h=maximum
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