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put this solution on YOUR website!Since v = i + j and w = - i + j, this means that v=<1,1> and w=<-1,1>
So their dot product is
v · w = 1*1+1*(-1) = 1 - 1 = 0
Since their dot product is equal to zero, this means that the two vectors are orthogonal (perpendicular)
Here's a picture to help visualize the problem and verify the answer: