2. This one seems harder than it really is
This function is odd [ it is symmetric about the orgin ] which means that if ( - a, - b) is on the graph....then so is (a, b)
So u (-2.72) leads to some - b
And u (2.72) leads to some b
So adding these together, we get -b + b = 0
The same logic will apply to u(-0.81) and u(0.81)
Adding their outputs will = 0
So
u(-2.72)+u(-0.81)+u(0.81)+u(2.72) = 0