已知:A+B=2a三次方+2a²-a-2,A-C=2a三次方-a-4a²+1 求绝对值a=3,代数式B+C的值
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![已知:A+B=2a三次方+2a²-a-2,A-C=2a三次方-a-4a²+1 求绝对值a=3,代数式B+C的值](/uploads/image/z/250272-0-2.jpg?t=%E5%B7%B2%E7%9F%A5%3AA%2BB%3D2a%E4%B8%89%E6%AC%A1%E6%96%B9%2B2a%26%23178%3B-a-2%2CA-C%3D2a%E4%B8%89%E6%AC%A1%E6%96%B9-a-4a%26%23178%3B%2B1+%E6%B1%82%E7%BB%9D%E5%AF%B9%E5%80%BCa%3D3%2C%E4%BB%A3%E6%95%B0%E5%BC%8FB%2BC%E7%9A%84%E5%80%BC)
已知:A+B=2a三次方+2a²-a-2,A-C=2a三次方-a-4a²+1 求绝对值a=3,代数式B+C的值
已知:A+B=2a三次方+2a²-a-2,A-C=2a三次方-a-4a²+1 求绝对值a=3,代数式B+C的值
已知:A+B=2a三次方+2a²-a-2,A-C=2a三次方-a-4a²+1 求绝对值a=3,代数式B+C的值
|a|=3
a²=3²=9
B+C=(A+B)-(A-C)
=2a³+2a²-a-2-(2a³-a-4a²+1)
=2a³+2a²-a-2-2a³+a+4a²-1
=(2a³-2a³)+(2a²+4a²)+(-a+a)-(2+1)
=6a²-3
当a²=9时
B+C=6×9-3
=54-3
=51