Đáp án + Giải thích các bước giải:
`a)40sqrt(25/6)-10sqrt(3/2)-12sqrt(98/3)`
`=40*sqrt25/sqrt6-10*sqrt3/sqrt2-12*sqrt98/sqrt3`
`=40*5/sqrt6-10*sqrt6/2-12*sqrt294/3`
`=40*(5sqrt6)/6-5sqrt6-4sqrt294`
`=(200sqrt6)/6-5sqrt6-4*7sqrt6`
`=(100sqrt6)/3-5sqrt6-28sqrt6`
`=(100sqrt6)/3-(15sqrt6)/3-(84sqrt6)/3`
`=sqrt6/3`
`b)` `M=2x sqrt(16xy^3)+7sqrt(25x^3y^3)-3y sqrt(36x^3y)(x>=0,y>=0)`
`=2xsqrt(16xy^2*y)+7sqrt(25*x^2y^2*xy)-3ysqrt(36x^2*xy)`
`=2x*4|y|sqrt(xy)+7*5|x||y|sqrt(xy)-3y*6|x|sqrt(xy)`
`=2x*4y*sqrt(xy)+7*5*x*y*sqrt(xy)-3y*6x*sqrt(xy)`
`=8xy*sqrt(xy)+35xy*sqrt(xy)-18xy*sqrt(xy)`
`=(8xy+35xy-18xy)*sqrt(xy)`
`=25xy*sqrt(xy)`.