MacFauz wrote:
1 & 2 together
a can be non zero while b and c could be 0. or
a can be 0 while b and c could be non zero. or
a,b & c all three can be 0.
So it is still not possible to determine whether a is zero or not.
Hence answer is E
Note: Look out for the case where b and c cannot be 0 at the same time. In that case, a must be 0.
e.g. the same question if slightly modified could result in (C)
In the xy-plane, does the line with the equation y=2x-4 contain the point (a,b)?
(1) (2a-b-4)(a+5b+2)=0
(2) (2a+10b-1)(2a-b-4)=0
From (1), (2a-b-4) = 0 OR (a+5b+2)=0 OR both are 0.
From (2), (2a-b-4)=0 OR (2a+10b-1)= 0 OR both are 0.
From no values of a and b, can (a+5b+2) and (2a+10b-1) be 0 simultaneously.
a + 5b + 2 = 0 implies a + 5b = -2
2a + 10b - 1 = 0 implies a + 5b = 1/2
a + 5b cannot take 2 different values at the same time. So (2a-b-4) must be 0.