Determine whether the following statement is true for every real numbers x and y: (x + y)^2 = x^2 + y^2
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Originally Posted by fancyface Determine whether the following statement is true for every real numbers x and y: (x + y)^2 = x^2 + y^2 No! If x=1, y=1 it is not true. --- But let find when it is true. --- Open paranthesis, x^2+2xy+y^2=x^2+y^2 Subtract, 2xy=0 Thus, xy=0 Thus, x=0 y=0 Now if we check these two we see that it is true! So this is true only when one of them is zero.
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