Which expression is equivalent to 7 A cubed open paren 6 A squared plus A close paren squared minus 4 A to the 6th power ?
A
252 A to the 7th power plus 80 A to the 6th power plus 7 A to the 5th powerB
252 A to the 7th power plus 84 A to the 6th power plus 7 A to the 5th powerC
252 A to the 7th power minus 4 A to the 6th power plus 7 A to the 5th powerD
252 A to the 7th power minus 4 A to the 6th power plus A squaredFirst square the binomial: (6A² + A)² = 36A⁴ + 12A³ + A². Multiplying by 7A³ gives 252A⁷ + 84A⁶ + 7A⁵; then subtracting 4A⁶ leaves 252A⁷ + 80A⁶ + 7A⁵. This matches choice A.
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