作业帮已知代数式（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]的值与X无关求3m²-[2m²-(4M+5+m]的值题打错了是（2Mx²-x²+3x+1)-[-(-5x²+4y²)+3x】
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![已知代数式（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]的值与X无关求3m²-[2m²-(4M+5+m]的值题打错了是（2Mx²-x²+3x+1)-[-(-5x²+4y²)+3x】](/uploads/image/z/1119834-18-4.jpg?t=%E5%B7%B2%E7%9F%A5%E4%BB%A3%E6%95%B0%E5%BC%8F%EF%BC%882Mx%26%23178%3B-x%26%23178%3B%2B3x%2B1%29-%5B-%285x%26%23178%3B%2B4y%26%23178%3B%29%2B3x%5D%E7%9A%84%E5%80%BC%E4%B8%8EX%E6%97%A0%E5%85%B3%E6%B1%823m%26%23178%3B-%5B2m%26%23178%3B-%284M%2B5%2Bm%5D%E7%9A%84%E5%80%BC%E9%A2%98%E6%89%93%E9%94%99%E4%BA%86%E6%98%AF%EF%BC%882Mx%26%23178%3B-x%26%23178%3B%2B3x%2B1%29-%5B-%28-5x%26%23178%3B%2B4y%26%23178%3B%29%2B3x%E3%80%91)
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已知代数式（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]的值与X无关求3m²-[2m²-(4M+5+m]的值题打错了是（2Mx²-x²+3x+1)-[-(-5x²+4y²)+3x】
已知代数式（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]的值与X无关
求3m²-[2m²-(4M+5+m]的值
题打错了是（2Mx²-x²+3x+1)-[-(-5x²+4y²)+3x】
已知代数式（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]的值与X无关求3m²-[2m²-(4M+5+m]的值题打错了是（2Mx²-x²+3x+1)-[-(-5x²+4y²)+3x】
解
原式=2mx^2 -x^2 +3x+1+(-5x^2 +4y^2)-3x
=2mx^2 -x^2 +3x+1-5x^2 +4y^2-3x
=(2m-6)x^2 +1+4y^2
所以
2m-6=0
解得 m=3
把m=3代入
3m²-[2m²-(4M+5+m]
=2m^2+5m+5
=18+15+5
=38
（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]
=2Mx²-x²+3x+1+5x²+4y²-3x
=x²(2m+4)+4y²+1
2m+4=0
m=-2
3m²-[2m²-(4M+5+m] 后半个小括号...
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（2Mx²-x²+3x+1)-[-(5x²+4y²)+3x]
=2Mx²-x²+3x+1+5x²+4y²-3x
=x²(2m+4)+4y²+1
2m+4=0
m=-2
3m²-[2m²-(4M+5+m] 后半个小括号在哪？
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