F.4 Maths 問題

9(y-2)²=(3-2y)²
(3y-6)² - (3-2y)² = 0
(3y-6+3-2y) (3y-6-3+2y) = 0
(y-3) (5y-9) = 0
y-3 = 0 or 5y-9 = 0
y = 3 or y = 9/5

2007-10-07 11:27:45 補充：
以上是用factor method做的。至於quadratic formula，先expand：9(y-2)²=(3-2y)² 9y²-36y＋36 = 9-12y＋4y² 5y²-24y＋27 = 0by quadratic formula:y = [-b±√(b²-4ac)]/2ay = [24±√(576-540)]/10y = (24±6)/10y = 30/10 or y = 18/10y = 3 or y = 9/5

9(y-2)²=(3-2y)²

首先要開方變成
3(y-2)=(3-2y)
3y-6=3-2y
3y+2y=3+6
5y=9
y=9/5