Make the subject of
Expand any brackets in your answer.
Identify what is currently attached to h. On the left, is divided by . To free it, apply the inverse operation to both sides: multiply by .
Multiply both sides by 4p. Keep the whole right-hand side in brackets — this is where the second term usually gets lost:
Expand the bracket as instructed. The factor multiplies each term inside:
Write the final rearranged formula.
Answering — multiplying only the first term — is the classic error the instruction 'expand any brackets' is designed to expose.
Check by reversing. Divide the answer by :
Test with numbers. Take and . The original right side is , so should be . The formula gives ✓.
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