MATHS!!

1.(3 x[2] - 5 y[2] ) - (6 y[2] - 2 z[2] ) + ( 7 z[2] + x[2] )
=3x[2] - 5y[2] - 6y[2] + 2z[2] + 7z[2] + x[2] <----拆括號
=3x[2] + x[2] - 5y[2] - 6y[2] + 2z[2] + 7z[2] <----把同類的數放在一起
=4x[2] - 11y[2] + 9z[2]

2.( x + 3y - 4z ) + ( 5x -8y + z ) - ( 6x + 2y + z )
=x + 3y - 4z + 5x - 8y + z - 6x - 2y - z
=x + 5x - 6x + 3y - 8y - 2y - 4z + z - z
= - 7y - 4z

3. 4y + 5x - 8x - 4y + 7x + 3y
=4y - 4y + 3y + 5x - 8x + 7x
=3y + 4x

同類的數eg. 5 and 8
eg1 5x and 8x
eg2 5x[2] and 8x[2] (次方必須一樣)

1. (3 x[2] - 5 y[2] ) - (6 y[2] - 2 z[2] ) + ( 7 z[2] + x[2] )
= 3x[2] - 5 y[2]- 6 y[2] + 2 z[2] + 7 z[2] + x[2]
=3x[2]+ x[2]- 5 y[2]- 6 y[2]+ 2 z[2] + 7 z[2]
=4x[2] -11y[2] + 9z[2]

2)( x + 3y - 4z ) + ( 5x -8y + z ) - ( 6x + 2y + z )
= x+3y - 4z + 5x - 8y +z -6x -2y -z
= x+5x-6x+3y - 8y -2y -4z + z -z
= -７y -4z

3) 4y + 5x - 8x - 4y + 7x + 3y
= 4y- 4y + 3y + 5x- 8x + 7x
= 3y + 4x

(其實做衣d數係有技巧嫁,開頭要拆哂ｄ括號，要變符號就變哂先，跟張一d同類既野擺埋一齊,x還x擺,y還y擺，ｚ還ｚ擺，相加減就易得多又唔容易計錯，做完仲方便你核對你做得岩唔岩!另外開頭做可能會有ｄ混亂ｏｒ唔係好識計，所以除左有技巧外，做多ｄ都係好要嫁！做熟ｄ見多ｄ題目，再遇到時候就諗得快ｄ同做得快ｄ嫁喇！　加油啦！）希望衣個方法幫到你啦！

1.
(3 x[2] - 5 y[2] ) - (6 y[2] - 2 z[2] ) + ( 7 z[2] + x[2] )
=3x^2-5y^2-6y^2+2z^2+7z^2+x^2
=4x^2-11y^2+9z^2+9

2.
( x + 3y - 4z ) + ( 5x -8y + z ) - ( 6x + 2y + z )
= x + 3y - 4z + 5x -8y + z - 6x- 2y - z
= -7y-4z

3.
4y + 5x - 8x - 4y + 7x + 3y
= 4x+3y