54-14xy-14+9y+2xy+7=
47-12xy+9y
(25x^2 − 14xy + 4) − (7x^2 − 9y) + (2xy + 7)
= 25x^2 − 14xy + 4 − 7x^2 + 9y + 2xy + 7
= 18x^2 - 12xy + 9y + 11
Hope it helps.
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