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Yahoo!奇摩知識+ - 分類問答 - 科學常識 - 已解決
Yahoo!奇摩知識+ - 分類問答 - 科學常識 - 已解決
國中數學的小地方疑問
Jun 18th 2013, 12:09

已經對於二元一次聯立方程式有概念了,
大約基本應用題部份是ok了,但還是有其他問題,如下:
(1)
y = 9/5y + 32 答案是 -40。
但不知道怎麼算?

(2)
若x = 3,y = -2,是ax+by=8的解,則6a-4b-5=?

代入後是 3a-2b = 8 然後乘上2→
6a-4b=16,在跟題目的6a-4b-5=?比較。
但我不懂為什麼答案會是11?怎麼算的?
兩個式子比較後怎麼寫?

(3)
如表,?的部份是不小心弄髒,每組代入都是方程式?x-3y=6的解。
x 0 (2) 3 -6 (4)
y(1) 0 4 (3) -4
我已經算出:
(1)= -2
(3)= -14......,
(2)應該是x-0=6,x=-6,但答案是1。
(4)應該是x+12=6,x=-6,但答案是-1。

是哪邊思考和觀念錯誤?請數學高手指導,謝謝。

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