Attempt the question, check the explanation, and continue with similar questions to build confidence before exams.
nCr * x^(n-r) * y^r
nCr * x^r * y^(n-r)
nCr * x^(n+r) * y^r
nCr * x^r * y^r
Continue with nearby questions to strengthen the same chapter concept while you still have the context fresh in mind.