What's the value of a^4 - b^4 ?
1. a^2 - b^2 = 16
2. a + b = 8
Appreciate it if somebody can help me in solving the above DS problem. An explanation will also be appreciated.
IMO C.a^4 - b^4 = (a^2 - b^2)*(a^2 + b^2)
1. a^2-b^2 = 16
. Clearly insufficient as we do not know the value of a^2+b^2
2. a+b = 8
. Again insufficient as it does not provide any information about value of a-b
Together 1 and 2 are sufficient. How???a^2-b^2 = 16(a-b)*(a+b) = 16a-b = 2
As we know that a+b = 8
. Now we can find the value of a & b
Thus answer is C.