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MathsF.2

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Linear Equation In Two Unknown1.Solve the following systems of equations by the method of substitution.(a) a+3b=18 (b)16w=5-4s 3a+5b=34 3s-8=8w+72.Solve the following systems of equations by the method of elimination.(a) 5x2y=6 3x+2y=10 3.A bag contains 60coins which are either $2 or $5... 顯示更多 Linear Equation In Two Unknown 1.Solve the following systems of equations by the method of substitution. (a) a+3b=18 (b)16w=5-4s 3a+5b=34 3s-8=8w+7 2.Solve the following systems of equations by the method of elimination. (a) 5x2y=6 3x+2y=10 3.A bag contains 60coins which are either $2 or $5 coins.The total value of the coins is $195.Find the number of the each type of coins. 4.The age of a boy exceeds one-third of his father's by 1. Five years later his age will be 4 less than half of his father's.What is the present age of his father? 更新: 更正2a: A. 5x-2y=6 3x+2y=10

最佳解答:

1a. a+3b=18 ...(1) 3a+5b=34 ...(2) a = 18 -3b ...(3) Sub (3) into (2) 3(18-3b) + 5b = 34 54 - 9b +5b = 34 -4b = -20 b = 5 Sub b=5 into (1) a + 3(5) = 18 a= 3 (b) 16w=5-4s ... (1) 3s-8=8w+7 ... (2) 16w = 5-4s w = (5-4s)/16 .....(3) Sub (3) into (2) 3s-8 = 8( (5-4s)/16) +7 3s-8 = (5-4s)/2 +7 6s-16 = 5-4s + 14 10s = 35 s = 3.5 Sub s=3.5 into (1) 16w = 5 - 4(3.5) 16w = 5 - 14 16w = -9 w = -9/16 w= -0.5625 2. (a) CANNOT SOLVE BY ELIMILATION TYPING ERROR??? 3. 2x +5y = 195 ...(1) x+y = 60 ... (2) x+y = 60 x = 60-y ... (3) Sub (3) into (1) 2(60-y) +5y = 195 120 -2y +5y = 195 3y = 75 y = 25 Sub y=25 into (2) x+ 25 = 60 x = 35 (Prove 2(35) + 5(25) 70 + 125 = 195 (OK) ) 4. B-1 = F x 1/3 ... (1) (b+5) +4 = (f+5) x 1/2 ...(2) b -1 = 1/3f b = 1/3f +1 ... (3) Sub (3) into (2) 1/3f +1 +5 +4 = (f+5) x 1/2 1/3f +10 = 1/2 f + 2.5 2f + 60 = 3f +15 f = 45 (Prove Sub f= 45 into (1) b-1 = 45 x 1/3 b-1 = 15 b = 16 Five years later b= 21 21+4 = (45+5 )x1/2 25 = 25 (OK) ) 2010-06-22 22:46:36 補充: A. 5x-2y=6 ... (1) 3x+2y=10 ... (2) (1) 5x - 2y = 6 +(2) 3x +2y = 10 ---------------------------------- 8x + 0y = 16 x = 2 Sub x=2 into (1) 5(2) -2y = 6 10 -2y = 6 2y = 4 y = 2 Prove 5(2) - 2(2) = 6 10- 4 = 6 (OK) 3(2) +2(2) = 10 6 +4 = 10 (OK)

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