rlz87tm45t的部落格

標題:

英文數學題

發問:

1.Solve the following systems of equations by the method of substitution. (a) a+3b=18 3a+5b=34 (b) 16w=5-4s 3s-8=8w+7 2.Solve the following systems of equations by the method of elimination. (a) 5x-2y=6 3x+2y=10

最佳解答:

1(a) a + 3b = 18 --> a = 18 - 3b sub a = 18 - 3b into 3a + 5b = 34***************** get: 3 * (18 - 3b) + 5b = 34 54 - 9b + 5b = 34 4b = 20 b = 5 // so, a = 18 - 3*(5) = 18 - 15 = 3 // (b) 16w = 5 - 4s --> 8w = 2.5 - 2s sub 8w = 2.5 - 2s into 3s - 8 = 8w + 7 get: 3s - 8 = 2.5 - 2s + 7 5s = 17.5 s = 3.5 // and 8w = 2.5 - 2*(3.5) = -4.5 so w = -0.5625 (or -9/16) // 2(a) 5x - 2y = 6 ---(1) 3x + 2y = 10 ---(2) (1)+(2): 5x + 3x = 6 + 10 8x = 16 x = 2 // sub x = 2 into (2) 3*(2) + 2y = 10 6 + 2y = 10 2y = 4 y = 2 //

• About Darcy's Equation@1@
• 魔界女王候補生會5會出第二輯
• 35元800分鐘電話儲值卡@1@

• About Darcy's Equation@1@
• 魔界女王候補生會5會出第二輯
• 35元800分鐘電話儲值卡@1@

 

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其他解答:

1a. a+3b=18-------1 3a+5b=34-----2 From 1, a=18-3b--------3 Substitute 3 into 2 3(18-3b)+5b=34 54-9b+5b=34 -4b=-20 b=5------4 Substitute 4 into 3 a=18-3(5) a=18-15 a=3 so a=3,b=5|||||1) a=18-3b sub. a=18-3b 3(18-3b)+5b=34 54-9b+5b=34 -9b+5b=34-54 -4b=-20 b=5 sub. b=5 a=18-3(5) a=3 Ans : a=3 & b=5