-7n(2次方)+57n+1660=0

-7n^2+57n+1660=0
7n^2-57n-1660=0
(7n+83)(n-20)=0
n=-83/7 or 20

-7n^2 + 57n + 1660 = 0
7n^2 - 57n - 1660 = 0
(7n + 83) (n - 20) = 0
7n + 83 = 0 or n - 20 = 0
7n = -83 or n = 20
n = -83/7 or n = 20

n=(-(57)±√(57×57-4(-7)(1660))÷2(-7)

n=(-57±223)÷(-14)

n=(-57+223)÷(-14) or n=(-57-223)÷(-14)

N=-166/14 n=20

Ans: (-7n^2-83)x(n-20)

-7n^2+57n+1660=0
n= [-(57)± √57^2-4(-7)(1660)]/2(17)
n=(-57± 223)/34
n=-11.85714 or 20

-7n(2次方)+57n+1660=0
7n(2次方)-57n-1660=0
(7n+20)(n-83)=0

n=-20/7 or n-83

2006-11-16 23:16:33 補充：
sorry. typed wrongly.(7n+83)(n-20)=0n=-83/7 or n=20