How do I prove that this is is true?

Question

#x^2 +y^2 >= 2xy# , #x# and #y# are real numbers.

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Answer 1 · 2017-12-02T13:28:17

see below

#AAx,y inRR#

#(x-y)^2>=0#

expanding the #LHS#

#x^2-2xy+y^2>=0#

#:.x^2+y^2>=2xy#