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以加減消元法解聯立方程 1.) 3x =5y-9, 5x=3y+1 2.) 2x-9y=20, 5x+4y= -3 3.) 5x+11y=43, -2x+3y=5 4.) 2y = x/5 +4, x+9y= -1 5.) x+y/4 =11, x/3 -y =- 5 6.) 7x+5y =3x+2y=-1 7.) 11x-3y-31 =4x+5x =-11 8.) 4x+y/3 = x+9y/2 =7 9.) 3x-7y/4 = 3x-2y/3 =-6 更新: 7.) 11x-3y-31 =4x+5x =-11 答案係x =1, y=-3 8.) 4x+y/3 = x+9y/2 =7 答案係x =5, y= 1 9.) 3x-7y/4 = 3x-2y/3 =-6 答案係 x = 26/5, y = 6/5
最佳解答:
1.) 3x =5y-9......(1) 5x=3y+1......(2) 5*(1),15x-25y=-45..(3) 3*(2),15x-9y=3......(4) (3)-(4),-16y=-48 y=3 代y=3入(2) 5x=3(3)+1 x=2 2.) 2x-9y=20..................(1) 5x+4y=-3.................(2) 5*(1),10x-45y=100...(3) 2*(2),10x+8y=-6.......(4) (4)-(3),53y=-106 y=-2 代y=-2入(2) 2x+9(2)=20 x=1 3.) 5x+11y=43.............(1) -2x+3y=5................(2) 2*(1),10x+22y=86...(3) 5*(2),-10x+15y=25..(4) (3)+(4),37y=111 y=3 代y=3入(2) -2x+3(3)=5 x=2 4.) 2y = x/5 +4...(1) x+9y= -1.......(2) 5*(1),10y=x+20 -x+10y=20.....(3) (2)+(3),19y=19 y=1 代y=1入(2) x+9=-1 x=-10 5.) x+y/4 =11...(1) x/3 -y =- 5...(2) 4*(1),4x+y=44...(3) (2)+(3),13x/3=39 x=9 代x=9入(3) 4*9+y=44 y=8 6.) 7x+5y =3x+2y=-1 7x+5y=1...(1) 3x+2y=1...(2) 2*(1),14x+10y=2....(3) 5*(2),15x+10y=5....(4) (4)-(3),x=3 代x=3入(2) 3*3+2y=1 y=-4 7.) 11x-3y-31 =4x+5x =-11 11x-3y-31=-11...(1) 4x+5x=-11...(2) 由(2) 9x=-11 x=-11/9 代x=-11/9入(1) 11(-11/9)-3y=20 y=-301/27 8.) 4x+y/3 = x+9y/2 =7 4x+y/3=7......(1) x+9y/2=7......(2) 4*(2),4x+18y=28...(3) (3)-(1),53y/3=21 y=63/53 代y=63/53入(3) 4x+18(63/53)=28 x=175/106 9.) 3x-7y/4 = 3x-2y/3 =-6 3x-7y/4=-6....(1) 3x-2y/3=-6....(2) (1)-(2),-13y/12=0 y=0 代y=0入(1) 3x=-6 x=-2 2015-01-12 19:05:04 補充： 第七至九題是否打錯題目???? 2015-01-12 19:09:52 補充： 7.) 11x-3y-31 =4x+5y =-11 11x-3y=20...(1) 4x+5y=-11...(2) 4*(1),44x-12y=80...(3) 11*(2),44x+55y=-121...(4) (4)-(3),67y=-201 y=-3 代y=-3入(2) 4x+5(-3)=-11 x=1 2015-01-13 18:16:24 補充： 8.) 4x+y/3 = x+9y/2 =7 4x+y/3=7......(1) x+9y/2=7......(2) 3*(1),4x+y=21...(3) 2*(2),x+9y=14...(4) 9*(3),36x+9y=189...(5) (5)-(4),35x=175 x=5 代x=5入(3) 4*5+y=21 y=1 2015-01-13 18:22:52 補充： 9.) 3x-7y/4 = 3x-2y/3 =-6 3x-7y/4=-6....(1) 3x-2y/3=-6....(2) 4*(1),3x-7y=-24...(3) 3*(2)3x-2y=-18...(4) (4)-(3),5y=6 y=6/5 代y=6/5入(4) 3x-2*6/5=-18 x=-26/5 2015-01-13 18:26:00 補充： 下次記得在合理的位置加返D括號，否則回答者會唔解你的意思。
其他解答:
http://i.imgur.com/yHY4dEk.jpg 第7至9題是圖片的第22題至24題 第9題(24題)是答案係 x = - 26/5, y = 6/5
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聯立方程 加減消元法發問:
以加減消元法解聯立方程 1.) 3x =5y-9, 5x=3y+1 2.) 2x-9y=20, 5x+4y= -3 3.) 5x+11y=43, -2x+3y=5 4.) 2y = x/5 +4, x+9y= -1 5.) x+y/4 =11, x/3 -y =- 5 6.) 7x+5y =3x+2y=-1 7.) 11x-3y-31 =4x+5x =-11 8.) 4x+y/3 = x+9y/2 =7 9.) 3x-7y/4 = 3x-2y/3 =-6 更新: 7.) 11x-3y-31 =4x+5x =-11 答案係x =1, y=-3 8.) 4x+y/3 = x+9y/2 =7 答案係x =5, y= 1 9.) 3x-7y/4 = 3x-2y/3 =-6 答案係 x = 26/5, y = 6/5
最佳解答:
1.) 3x =5y-9......(1) 5x=3y+1......(2) 5*(1),15x-25y=-45..(3) 3*(2),15x-9y=3......(4) (3)-(4),-16y=-48 y=3 代y=3入(2) 5x=3(3)+1 x=2 2.) 2x-9y=20..................(1) 5x+4y=-3.................(2) 5*(1),10x-45y=100...(3) 2*(2),10x+8y=-6.......(4) (4)-(3),53y=-106 y=-2 代y=-2入(2) 2x+9(2)=20 x=1 3.) 5x+11y=43.............(1) -2x+3y=5................(2) 2*(1),10x+22y=86...(3) 5*(2),-10x+15y=25..(4) (3)+(4),37y=111 y=3 代y=3入(2) -2x+3(3)=5 x=2 4.) 2y = x/5 +4...(1) x+9y= -1.......(2) 5*(1),10y=x+20 -x+10y=20.....(3) (2)+(3),19y=19 y=1 代y=1入(2) x+9=-1 x=-10 5.) x+y/4 =11...(1) x/3 -y =- 5...(2) 4*(1),4x+y=44...(3) (2)+(3),13x/3=39 x=9 代x=9入(3) 4*9+y=44 y=8 6.) 7x+5y =3x+2y=-1 7x+5y=1...(1) 3x+2y=1...(2) 2*(1),14x+10y=2....(3) 5*(2),15x+10y=5....(4) (4)-(3),x=3 代x=3入(2) 3*3+2y=1 y=-4 7.) 11x-3y-31 =4x+5x =-11 11x-3y-31=-11...(1) 4x+5x=-11...(2) 由(2) 9x=-11 x=-11/9 代x=-11/9入(1) 11(-11/9)-3y=20 y=-301/27 8.) 4x+y/3 = x+9y/2 =7 4x+y/3=7......(1) x+9y/2=7......(2) 4*(2),4x+18y=28...(3) (3)-(1),53y/3=21 y=63/53 代y=63/53入(3) 4x+18(63/53)=28 x=175/106 9.) 3x-7y/4 = 3x-2y/3 =-6 3x-7y/4=-6....(1) 3x-2y/3=-6....(2) (1)-(2),-13y/12=0 y=0 代y=0入(1) 3x=-6 x=-2 2015-01-12 19:05:04 補充： 第七至九題是否打錯題目???? 2015-01-12 19:09:52 補充： 7.) 11x-3y-31 =4x+5y =-11 11x-3y=20...(1) 4x+5y=-11...(2) 4*(1),44x-12y=80...(3) 11*(2),44x+55y=-121...(4) (4)-(3),67y=-201 y=-3 代y=-3入(2) 4x+5(-3)=-11 x=1 2015-01-13 18:16:24 補充： 8.) 4x+y/3 = x+9y/2 =7 4x+y/3=7......(1) x+9y/2=7......(2) 3*(1),4x+y=21...(3) 2*(2),x+9y=14...(4) 9*(3),36x+9y=189...(5) (5)-(4),35x=175 x=5 代x=5入(3) 4*5+y=21 y=1 2015-01-13 18:22:52 補充： 9.) 3x-7y/4 = 3x-2y/3 =-6 3x-7y/4=-6....(1) 3x-2y/3=-6....(2) 4*(1),3x-7y=-24...(3) 3*(2)3x-2y=-18...(4) (4)-(3),5y=6 y=6/5 代y=6/5入(4) 3x-2*6/5=-18 x=-26/5 2015-01-13 18:26:00 補充： 下次記得在合理的位置加返D括號，否則回答者會唔解你的意思。
其他解答:
http://i.imgur.com/yHY4dEk.jpg 第7至9題是圖片的第22題至24題 第9題(24題)是答案係 x = - 26/5, y = 6/5
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