very tough combination VIC og 122

resilient · Posted: Thu Feb 07, 2008 9:59 pm Post subject: very tough combination VIC og 122

an operation # is defined by the equation a#b = a-b/a+b, for all numbers a dn b such that a not equa -b. If a not equal -c and a#c=0, then c=

a. -a
b.-1/a
c. 0
d. 1/a
e. a

Saffa · Posted: Fri Feb 08, 2008 3:13 am Post subject:

for a#c to be equal to zero and a <> -c, the numerator of the equation needs to be equal to zero.

i.e. because a#c = (a-c)/(a+c) and a+c is not equal to (<>) 0

The the following ust be true

a - c = 0
ie. a = c

blue_lotus · Posted: Fri Feb 08, 2008 5:30 am Post subject:

If the fraction has to become 0 the numerator must be 0
in this case the numerator is a-c =0
which means a=c , hence the answer

Other information like a not equal to -c , is given to ensure the denominator is not zero. If denominator is zero the fraction becomes undefined.