Question

Factorise :- y²-18xy-63x².​

Answer 1

Answer:

(y)² - 2×y×9x + 81x² -144x²

=(y)² - 2×y×9x + (9x)² -(12x)²

= (y-9x)² -(12x)²

= {(y-9x)+12x}{(y-9x)-12x}

= (y-9x+12x)(y-9x-12x)

=( y + 3x)(y-21x)

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