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Original eqn: - (m^4x^5)/k^5 + (2m^2x^5)/(k^5m^-2) -(3m^3x^2k)/(m^-4x^3k^4)

find a common denominator - in this case, k^5. so multiply the second term by (m^2/m^2) which is just multiplying by 1! multiply the third term by (m^4x^-3)/(m^4x^-3), again just multiplying by 1