標題:
F.2Maths!!!!!!!!!!!20p!!!!!!
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發問:
(use the method of elimination) 1) 3x+2y=2 4x-3y=-20 2)The sum of two no. is 53 and the difference of the two no. is5.Findthe two no. Solution:Let x be the larger number and y be the smaller number.
最佳解答:
1) 3x + 2y = 2... (1) 4x – 3y = -20 … (2) (1) x 3 => 9x + 6y = 6 … (3) (2) x 2 => 8x – 6y = -40 … (4) (3) + (4) => 17x = -34 x = -2 Sub into (1), (3)(-2) + 2y = 2 2y – 6 = 2 2y = 8 y = 4 2) Let x be the larger number and y be the smaller number. x + y = 53 … (1) x – y = 5 … (2) (1) + (2) => 2x = 58 x = 29 Sub into (1), 29 + y = 53 y = 24 The two numbers are 24 and 29
其他解答:
1) 3x+2y=2_________________(1) 4x-3y=-20________________(2) Form (1),we have 3x=2-2y x=1/3 (2-2y)_______________________(3) Subst. (3) into (2),we have 4[1/3 (2-2y)]-3y=-20 4(2-2y)-9y=-60 8-8y-9y=-60 -17y=-68 y=4 Subst. y=4 into (1),we have 3x+2(4)=2 3x+8=2 3x=-6 x=-2 2.Let x be the larger number and y be the smaller number. x+y=53__________________________(1) x-y=5___________________________(2) (1)+(2):2x=58 x=29 Subst. x=29 into (1) (29)+y=53 y=24 2009-08-27 20:49:16 補充： 慢了...
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