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Question
Show that: (3x + 7)2 − 84x = (3x − 7)2
Solution
\[ \text { LHS } = \left( 3x + 7 \right)^2 - 84x\]
\[ = \left( 3x + 7 \right)^2 - 4 \times 3x \times 7\]
\[ = \left( 3x - 7 \right)^2 \left[ \because \left( a + b \right)^2 - 4ab = \left( a - b \right)^2 \right]\]
= RHS
Because LHS is equal to RHS, the given equation is verified.
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