colakumarfanta wrote:IS a^2 + b^2 >= 1?
1. A + b >= 1
2.a^2 - b^2 >= 1

IMO B

st 1:

a +b >=1

Plugging in numbers for(a,b)

case 1: {1/2, 1/2}.

a^2 + b^2 >= 1 --------NO


case 2:(1,1)

a^2 + b^2 >= 1 ---YES

Inconsistent answers.

Insufficient

st 2 : a^2 - b^2 >= 1

a^2 >= 1+b^2

substitute this value of a^2 in main equation:

a^2 + b^2

1+b^2 + b^2 >=1

try some plugging in numbers :
b =0 --> a= 1--> a^2 + b^2 >= 1 --YES

b= -2---> a=5--> a^2 + b^2 >= 1----yes

IMO B

From 1 we get a^2+b^2>=1-2ab..not sufficient
From 2 a^2-b^2>=1..
so we can conclude a^2>=1 and b^2>=0
hence a^2+b^2>=1...sufficient

Ans option B
What is OA?

QA : B