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下列计算正确的是 ( )
a 6 + a 6 = 2 a 12
2 - 2 ÷ 2 0 × 2 3 = 32
( - 1 2 a b 2 ) · ( - 2 a 2 b ) 3 = a 3 b 3
a 3 · ( - a ) 5 · a 12 = - a 20
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