(1)填写多项式各项及其系数和次数(2)若多项式是7次多项式,求m的值.多项式4x^2m+1 乘以y-5x^2乘以y^2-兀x^5乘以y4x^2m+1 乘以y 系数4；次数2m+1+1=2m+2；-5x^2乘以y^2 系数-4；次数2+2=4；-兀x^5乘以y 系数-π；次数=...