√(x^5+x^4y²) = x² √(x+y²)
√(a^5+2a³b²+ab^4) = √{a(a²+b²)² } = (a²+b²) √a
√(12x²y+24x²+y³) = 最后一题有误,如果是：
√(12x²y+36x²y+y³) =√(36x²y+12x²y+y³) =√{y(6x+y)²} = |6x+y| √y√(12x²y+24x²y³)√(12x²y+24x²y³)= √{4x²(3y+6y³) = 2|x|√(3y+6y³)