作业帮先化简,再求值1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a},其中a=5分之12.已知M=2x²+3kx-2x+6,N=-x²+kx+2,且3M+6N的值与X无关,求k的值
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![先化简,再求值1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a},其中a=5分之12.已知M=2x²+3kx-2x+6,N=-x²+kx+2,且3M+6N的值与X无关,求k的值](/uploads/image/z/13829298-42-8.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC1.18a%26%23178%3B-%7B-6a%26%23178%3B%2B%5B5a-4a%26%23178%3B-%28a%26%23178%3B-2a%26%23178%3B%29%5D%2B15a%26%23178%3B-5a%7D%2C%E5%85%B6%E4%B8%ADa%3D5%E5%88%86%E4%B9%8B12.%E5%B7%B2%E7%9F%A5M%3D2x%26%23178%3B%2B3kx-2x%2B6%2CN%3D-x%26%23178%3B%2Bkx%2B2%2C%E4%B8%943M%2B6N%E7%9A%84%E5%80%BC%E4%B8%8EX%E6%97%A0%E5%85%B3%2C%E6%B1%82k%E7%9A%84%E5%80%BC)
先化简,再求值1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a},其中a=5分之12.已知M=2x²+3kx-2x+6,N=-x²+kx+2,且3M+6N的值与X无关,求k的值
先化简,再求值
1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a},其中a=5分之1
2.已知M=2x²+3kx-2x+6,N=-x²+kx+2,且3M+6N的值与X无关,求k的值
先化简,再求值1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a},其中a=5分之12.已知M=2x²+3kx-2x+6,N=-x²+kx+2,且3M+6N的值与X无关,求k的值
1.18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a}
=18a²-{-6a²+[5a-4a²-a²+15a²-5a}
=18a²-{-6a²+10a²}
=14a²
当a=1/5时,原式=14×1/25=14/25
2.3M+6N
=3（2x²+3kx-2x+6）+6（-x²+kx+2）
=6x²+9kx-6x+18-6x²+6kx+12
=(15k-6)x+30
∵3M+6N的值与X无关
∴15k-6=0
k=2/5
1. 18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a}
=18a²+6a²-5a+4a²+a²-2a²-15a²+5a
=11a²
=11/25
2. 3M+6N=3(2x²+3kx...
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1. 18a²-{-6a²+[5a-4a²-(a²-2a²)]+15a²-5a}
=18a²+6a²-5a+4a²+a²-2a²-15a²+5a
=11a²
=11/25
2. 3M+6N=3(2x²+3kx-2x+6)+6(-x²+kx+2)
=6x²+9kx-6x+18-6x²+6kx+12
=(15k-6)x+30
因为3M+6N的值与X无关,所以
15k-6=0
则k=6/15=2/5
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