bài 2: thực hiện phép tính
tks mn ạ
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\(a,=-15x^3+10x^4+20x^2\\ b,=2x^3+2x^2+4x-x^2-x-2=2x^3+x^2+3x-2\)
\(a,\dfrac{-13}{5}-\dfrac{-7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\\ =\dfrac{-13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\\ =\dfrac{-77}{45}+\dfrac{4}{5}\\ =\dfrac{-41}{45}\\ b.\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\\ =\left(\dfrac{68}{9}+\dfrac{8}{3}\right)-\dfrac{47}{9}\\ =\dfrac{92}{9}-\dfrac{47}{9}\\ =5\)
2)\(-\dfrac{13}{5}--\dfrac{7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{7.15.8}{15.9.7}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\)
\(=\left(-\dfrac{13}{5}+\dfrac{4}{5}\right)+\dfrac{8}{9}\)
\(=-\dfrac{9}{5}+\dfrac{8}{9}\)
\(=\dfrac{-81+40}{45}=-\dfrac{41}{45}\)
3)\(\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\)
\(=\left(7\dfrac{5}{9}-5\dfrac{2}{9}\right)+2\dfrac{2}{3}\)
\(=2\dfrac{1}{3}+2\dfrac{2}{3}\)
\(=5\)
Bài 2:
a: \(\Leftrightarrow x:\dfrac{4}{5}=\dfrac{-4}{6}+\dfrac{3}{6}=\dfrac{-1}{6}\)
=>x=-1/6*4/5=-4/30=-2/15
b: =>1/6x=5/6-7/12+1/3=10/12-7/12+4/12=7/12
=>x=7/2
c: =(47/11-3x)*11/5=-21/5
=>47/11-3x=-21/5:11/5=-21/11
=>3x=68/11
=>x=68/33
-472 + (235 - 28) - (35 - 350)
= -472 + 235 - 28 - 35 + 350
= (-472 - 28) + (235 - 35) + 350
= -500 + 200 + 350
= -500 + 550
= 50