gpjqem1的部落格

標題:

• 班拿約o唔ok-@1@
• 偵探學園Q真人版 (10分)@1@
• 請問數學的unit c.c. 是什麼意思-@1@

 

此文章來自奇摩知識+如有不便請留言告知

二元一次方程10點(緊急)thx

發問:

4y+3x+2z=45 3y+2x+4z=33 2y+4x+3z=30 x=? y=? z=?

最佳解答:

4y+3x+2z=45 --- (1) 3y+2x+4z=33 ---(2) 2y+4x+3z=30 ---(3) (1) + (2) +(3) 9y + 9x + 9z = 108 y+x+z = 12 --(4) (4) x 4 4y + 4x + 4z = 48 --(5) (5) - (1) x + 2z = 3 ---(6) (4) x 3 3x + 3y + 3z = 36 (5)' (5)' - (2) x - z = 3 ---(7) (6) - (7) 3z = 0 z = 0 sub. into (7) x = 3 sub. into(4) y = 9

其他解答:

x = 3, y = 9, z = 0|||||4y + 3x + 2z = 45 ...........(1) 3y + 2x + 4z = 33 ...........(2) 2y + 4x + 3z = 30 ...........(3) (1)*2 - (2) (4y + 3x + 2z)*2 - (3y + 2x + 4z) = 45*2 - 33 8y + 6x + 4z - 3y - 2x - 4z = 57 5y + 4x = 57 ................(4) (1)*3 -(3)*2 (4y + 3x + 2z)*3 - (2y + 4x + 3z)*2 = 45*3 - 30*2 12y + 9x + 6z - 4y - 8x - 6z = 75 8y + x = 75 ...............(5) (5)*4 - (4) (8y + x)*4 - (5y + 4x)= 75*4 - 57 32y + 4x - 5y - 4x = 243 27y = 243 y = 9 Put y = 9 into (5) 8*9 + x = 75 72 + x = 75 x = 3 Put x = 3, y = 9 into (1) 4*9 + 3*3 + 2z = 45 36 + 9 + 2z = 45 z = 0 Therefore, x = 3, y = 9, z = 0|||||4y+3x+2z=45-------------1 3y+2x+4z=33-------------2 2y+4x+3z=30-------------3 (3)*2-1 4y+8x+6z-4y-3x-2z=30*2-45 4z=15-5x------------4 z=(15-5x)/4-----------5 put 4 into 2 3y+2x+15-5x=33 y=6+x-----------------6 put 5,6 into 1 4(6+x)+3x+(15-5x)/2=45 x=3 put x = 3 into 6 y=9 put x=3 into 5 z=0