\(A=2020\cdot2018-2019^2\)

\(\Leftrightarrow A=\left(2019+1\right)\left(2019-1\right)-2019^2\)

\(\Leftrightarrow A=2019^2-1-2019^2\)

\(\Leftrightarrow A=-1\)

À, cái này là dùng hằng đẳng thức của lớp 8 á ^^

Học tốt!!!

#Bo

A=2020.2018-2019²

A=2020.2018.2019-2019

A=(2019+1).2018-2019.2019

A=2019.2018+2018-2019.2019

A=2019.(2019-1)+2018-2019.2019

A=2019.2019-2019+2018-2019.2019

A=2019.2019-(2019-2018)-2019.2019

A=2019.2019-1-2019.2019

A=(-1)

Mk ko chắc làm đúng đâu sai thì xl bn nhiều

\(\frac{-1}{3}:\frac{-5}{6}=\frac{-1}{3}\times\frac{-6}{5}=\frac{2}{5}\)

@muối

(-1/3) : (-5/6) = 2/5

\(\frac{-1}{3}:\frac{-5}{6}\)

\(=\frac{-1}{3}.\frac{6}{-5}\)

\(=\frac{-6}{-15}\)

\(=\frac{-2}{-5}\)

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

\(a,=73.\left(34+1+65\right)=73.100=7300\\ b,=-\left(45+35\right)=-80\\ c,=299-6\left(14:5-3\right)=299-6\left(-\dfrac{1}{5}\right)=299+\dfrac{6}{5}=\dfrac{1501}{5}\)

1.
a) 73.34+73+73.65
= 73.34+73.1+73.65 (bạn có thể thêm bước này nếu bạn muốn)
= 73.(34+1+65)
= 73.100
= 7300
b) (-45)+(-35)
= -80 (vì trừ cộng trừ ra trừ)
c) 299-6[(12+2):5-3]
= 299-6(14:2)
= 299-6.7
= 299-42
= 257

a: =-(3,54+4,783)=-8,323

b: =23-10=13

c: Sửađề: (-2,86)*4,2-3,14*4,2-6*32

=4,2(-2,86-3,14)-192

=-4,2*6-192

=-25,2-192

=-217,2

c: \(=5+\dfrac{6}{7}-2-\dfrac{3}{8}-1-\dfrac{1}{8}=2+\dfrac{6}{7}-\dfrac{1}{2}=\dfrac{3}{2}+\dfrac{6}{7}=\dfrac{33}{14}\)

e: \(=\dfrac{-3}{5}\left(-\dfrac{1}{9}-\dfrac{5}{6}+\dfrac{5}{2}\right)=\dfrac{-3}{5}\cdot\dfrac{14}{9}=\dfrac{-14}{15}\)

\(112\cdot35+112\cdot65+800\)

\(=112\cdot\left(35+65\right)+800\)

\(=112\cdot100+800\)

\(=11200+800\)

\(=12000\)