Question
Expand the following, using suitable identities. $(2x + 9)(2x - 7)$
✓
Answer
$(2x + 9)(2x - 7)$
$= (2x + 9)[2x + (-7)]$
$= (2x)^2+ [9 + (-7)] 2x + 9 × (-7)$
$= 4x^2+ 4x - 6$
$= (2x + 9)[2x + (-7)]$
$= (2x)^2+ [9 + (-7)] 2x + 9 × (-7)$
$= 4x^2+ 4x - 6$
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