Q1 of 36 Page 24

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(9x – 5l)(9x + 3l)

(9x – 5l)(9x + 3l)=(9x)2 + [(- 5l)+(3l)] 9x + [(- 5l)×(3l)]


{ ∵(x + a)(x + b)= x2 +(a + b)x +(a × b)}


= 81x2 + [(- 2l)×(9x)] +(- 15l2)


= 81x2 – 18xl – 15l2


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