You can put this solution on YOUR website! [p^2/2mr^2] - [gmM/r]
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lcd = 2mr^2
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Rewrite each fraction with the lcd as its denominator:
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[p^2/lcd] - [gmM(2mr)/lcd]
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Combine the numerators over the gcd:
[p^2 - 2gm^2Mr].cd
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[p^2 - 2gm^2Mr]/(2mr^2)
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Cheers,
Stan H.