Question 140

The missing term which makes the following a perfect square is
81 $$ X^{2} $$ - 72 xy + ____

Solution

(9x)$$^{2}$$-2×(9x)×(4y) + (4y)$$^{2}$$

=(9x-4y)$$^{2}$$ which is a perfect square.

Thus, if the missing term is 16y$$^{2}$$, the expression will be a perfect square.

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