1. 12(x+33)= x^2 -9
2 (x-3)^2 +(2x+1)(2-x)=0
(give the ans to 3 sign.fig if necessary.)
show steps please!
Thx so much
really want to know the methods to solve them
Attention: I am not asking for hw but for my test, thx:]
ans 1. -15, 27
2. -5.14 ,2.14
Quadratic equations
2012-09-11 5:09 am
回答 (1)
2012-09-11 6:10 am
✔ 最佳答案
首先，對於 ax^2+bx+c=0，解是http://upload.wikimedia.org/wikipedia/zh/math/0/f/1/0f16872ccd04ca7ecce3544bc3521ff1.png
知道這點，開始計算~
1)
12(x+33)= x^2 -9
12x+12*33=x^2-9
12x+396=x^2-9
x^2-12x-9-396=0
x^2-12x-405=0
x= -15,27
2)
(x-3)^2 +(2x+1)(2-x)=0
x^2-2(x)(3)+3^2+4x+2-2x^2-x=0
-x^2-3x+11=0
x=-5.14 ,2.14 (3sf)
如果題目不指定method of completing the square，只需要代公式就ok。
參考: me
收錄日期: 2021-04-13 18:57:53
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120910000051KK00600