[tex]a)\\\\5a\cdot6b-2\cdot(-5a)+2a\cdot3-b\cdota =30ab+10a +6a - ab=29ab+16a[/tex]
[tex]b)\\\\a^2b\cdot b+aba-2abba-a^2*(-4b)=a^2b^2+a^2b -2a^2b^2+4a^2b =5a^2b-a^2b^2[/tex]
[tex]c)\\\\ st^2\cdot(-2s)-3st(-5t)+2s^2\cdot3t-t^2\cdot(-s) = -2s^2t^2+15st^2 +6s^2t+st^2=\\\\= -2s^2t^2 +6s^2t+16st^2[/tex]
[tex]d)\\\\ -3x\cdot(-2)y+4x\cdot(-3xy)+2y\cdot(-x)-x^2\cdot(-5y)=6xy-12x^2y-2xy+5x^2y=\\\\=4xy-7x^2y[/tex]
[tex]e)\\\\ pr\cdot3p^2r-(-rp)\cdot(-2pr)+3\cdotprprp-r^2\cdot4pp = 3p^3r^2-2 p^2r^2+3p^3r^2-4p^2r^2=\\\\=6p^3r^2-6p^2r^2[/tex]
[tex]f)\\\\2x\cdot(-5x)y-7\cdot(-3xy)+2xy\cdot3x-(-4xy)\cdot(-2)= -10x^2 y+21xy +6x^2y -8xy=\\\\=13xy-4x^2y[/tex]
