Q2 of 36 Page 28

Simplify

(3k – 4r – 2m)2 -(3k + 4r – 2m)2

(3k – 4r – 2m)2 -(3k + 4r – 2m)2 = [(3k)2 +(- 4r)2 + (- 2m)2 +{2 ×(3k)×(- 4r)} +{2 ×(- 4r)× (-2m)} +{2 ×(3k)×(- 2m)} ] - [(3k)2 + (4r)2 +(- 2m)2 +{2 ×(3k)×(4r)} +{2 × (4r)×(- 2m)} +{2 ×(3k)×(-2m)} ]


{ (a + b +c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac }


= [ 9k2 + 16r2 + 4m2+{ – 24kr} +{16rm } +{ – 12km } ] - [ 9k2 + 16r2 + 4m2 +{24kr } +{– 16rm } + { – 12km } ]


= [ 9k2 + 16r2 + 4m2 – 24kr + 16rm – 12km ] - [ 9k2 + 16r2 + 4m2 + 24kr – 16rm – 12km ]


= 9k2 + 16r2 + 4m2 – 24kr + 16rm – 12km – 9k2 – 16r2 – 4m2 – 24kr + 16rm + 12km


= - 48kr + 32rm


= 32rm – 48kr


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