Maths

x^2 + ax + 48 = (x+y)(x+z)
x^2 + ax + 48 = x^2 + (y+z)x + yz
So a = y+z and yz = 48
The maximum value of a = y+z = 1 + 48 = 49(when yz = 1*48);
x^2 - 8x - c = (x+m)(x+n) = x^2 + (m+n)x + mn
So - 8 = m+n and c = - mn
The maximum value of c = - (-50)(42) = 2100(when m+n = -50+42 = - 8)
The maximum value of ac = 48 * 2100 = 100800


2009-12-07 17:10:58 補充：
Corrections:

The maximum value of ac = 49 * 2100 = 102900

Sorry!

2009-12-07 17:11:29 補充：
Corrections:

The maximum value of ac = 49 * 2100 = 102900

Sorry!