標題:
F.4 2題數學唔識做!! help!!! 高手!!
發問:
1.If the price of an apple rises by $1,then 4 fewer apples could be bought for $80.find the original price of an apple. 2.If the product of two consecutive number is 56,find the two number 詳細解答 pls !!!
1)16 80/4 -4*1 2)let x be the smallest number x(x+1)=56 x^2+x-56=0 (x+8)(x-7)=0 x=7 or -8 (reject) so the smallest number is 7 i.e. the consecutive number are 7 and 7+1=8
其他解答:
1)Let the original price be x 80/x - 80/(x+1) = 4 <<< (80/x is the number of apples that could be bought) (80x + 80 - 80x)/(x^2 + x) = 4 80 = 4x^2 + 4x x^2 + x - 20 = 0 (x+5)(x-4) = 0 x = -5 (rej) or 4 The original price is $4 2) Let the smaller number be x x(x+1) = 56 x^2 + x - 56 = 0 (x+8)(x-7) = 0 x = -8 or 7 The pairs of numbers are (-8 and -7) or (7 and 8)
F.4 2題數學唔識做!! help!!! 高手!!
發問:
1.If the price of an apple rises by $1,then 4 fewer apples could be bought for $80.find the original price of an apple. 2.If the product of two consecutive number is 56,find the two number 詳細解答 pls !!!
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最佳解答:1)16 80/4 -4*1 2)let x be the smallest number x(x+1)=56 x^2+x-56=0 (x+8)(x-7)=0 x=7 or -8 (reject) so the smallest number is 7 i.e. the consecutive number are 7 and 7+1=8
其他解答:
1)Let the original price be x 80/x - 80/(x+1) = 4 <<< (80/x is the number of apples that could be bought) (80x + 80 - 80x)/(x^2 + x) = 4 80 = 4x^2 + 4x x^2 + x - 20 = 0 (x+5)(x-4) = 0 x = -5 (rej) or 4 The original price is $4 2) Let the smaller number be x x(x+1) = 56 x^2 + x - 56 = 0 (x+8)(x-7) = 0 x = -8 or 7 The pairs of numbers are (-8 and -7) or (7 and 8)
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