Factorise x2y2 – xy – 72

(i) x2y2 – xy – 72

(ii) 9x3y + 41x2y2 + 20xy3

Answer :

(i) x2y2 – xy – 72

x2y2 – 9xy + 8xy – 72

Take out common in all terms,

xy(xy – 9) + 8(xy – 9)

(xy – 9) (xy + 8)

(ii) 9x3y + 41x2y2 + 20xy3

9x3y + 41x2y2 + 20xy3

Take out common in all terms,

xy(9x2 + 41xy + y2)

Above terms can be written as,

xy (9x2 + 36xy + 5xy + 20y2)

xy [9x(x + 4y) + 5y(x + 4y)]

xy (x + 4y) (9x + 5y)

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