`a)`

`@A(x)=5x-8x+2x^2-9x^3+1`

  `A(x)=-9x^3+2x^2-3x+1`

`@B(x)=x^3-5x-2x^2+6x-2`

  `B(x)=x^3-2x^2+x-2`

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`b)A(x)+B(x)=-9x^3+2x^2-3x+1+x^3-2x^2+x-2`

                 `=-8x^3-2x-1`

___________________________________________________

`c)A(x)-B(x)=-9x^3+2x^2-3x+1-x^3+2x^2-x+2`

                `=-10x^3+4x^2-4x+3`

a)\(A\left(x\right)=-9x^3+2x^2-3x+1\)

\(B\left(x\right)=x^3-2x^2+x-2\)

b)\(A\left(x\right)+B\left(x\right)=9x^3+2x^2-3x+1+x^3-2x^2+x-2\)

\(A\left(x\right)+B\left(x\right)=-8x^3-2x-1\)

c)\(A\left(x\right)-B\left(x\right)=-9x^3+2x^2-3x+1-x^3+2x^2-x+2\)

\(A\left(x\right)-B\left(x\right)=-10x^3+4x^2-4x+3\)

\(a,3x+17=-5\\ \Rightarrow3x=-22\\ \Rightarrow x=-\dfrac{22}{3}\\ b,\dfrac{-5}{8}=\dfrac{x}{16}\\ \Rightarrow x=\dfrac{-5}{8}.16\\ \Rightarrow x=-10\\ c,\dfrac{4}{9}+\dfrac{7}{3}:x=\dfrac{1}{5}\\ \Rightarrow\dfrac{7}{3}:x=-\dfrac{11}{45}\\ \Rightarrow x=-\dfrac{105}{11}\)

\(a)3.x+17=-5\)

\(3.x\)         \(=\left(-5\right)-170=-22\)

  \(x\)          \(=\left(-22\right)\div3\)

  \(x\)          \(=\dfrac{-22}{3}\)

\(b)\dfrac{-5}{8}=\dfrac{x}{16}\)

\(\Rightarrow x=\dfrac{\left(-5\right)\times16}{8}=\dfrac{-80}{8}=-10\)

\(c)\dfrac{4}{9}+\dfrac{7}{3}:x=\dfrac{1}{5}\)

           \(\dfrac{7}{3}:x=\dfrac{1}{5}-\dfrac{4}{9}\)

           \(\dfrac{7}{3}:x=\dfrac{1}{5}+\left(\dfrac{-4}{9}\right)=\dfrac{9}{45}+\left(\dfrac{-20}{45}\right)=\dfrac{-11}{45}\)

                 \(x=\dfrac{7}{3}:\left(\dfrac{-11}{45}\right)=\dfrac{7}{3}\times\left(\dfrac{-45}{11}\right)\)

                 \(x=\dfrac{-315}{33}=\dfrac{-105}{11}\)

tự kể màk

\(=\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}=\dfrac{5}{2}\)

h,=\(\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}\)

=\(\left(\dfrac{7}{10}.20\right).\left(\dfrac{8}{3}.\dfrac{3}{8}\right).\dfrac{5}{28}\)

=\(14.1.\dfrac{5}{28}\)

=\(14.\dfrac{5}{28}\)

=\(\dfrac{5}{2}\)

\(0,7.2\dfrac{2}{3}.20.0,375.\dfrac{5}{28}\) 

\(=\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}\) 

\(=\left(\dfrac{7}{10}.20.\dfrac{5}{28}\right).\left(\dfrac{8}{3}.\dfrac{3}{8}\right)\) 

\(=\dfrac{5}{2}.1\) 

\(=\dfrac{5}{2}\)

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