\(A=\frac{8056}{2012.16-1982}\)= \(\frac{2014.4}{2012.15+2012-1982}\)=\(\frac{2014.4}{2012.15+30}\)=\(\frac{2014.4}{2012.15+2.15}\)=\(\frac{2014.4}{15.\left(2012+2\right)}=\frac{2014.4}{15.2014}=\frac{4}{15}\)

B = \(\frac{1.2.6+2.4.12+4.8.24+7.14.42}{1.6.9+2.12.18+4.24.36+7.42.63}\)

= \(\frac{1.2.3.2+2.2.2.12+4.4.2.24+7.7.2.42}{1.2.3.9+2.12.2.9+4.24.4.9+7.42.7.9}\)

= \(\frac{2\left(1.2.3+2.2.12+4.4.24+7.7.42\right)}{9\left(1.2.3+2.2.12+4.4.24+7.7.42\right)}\)

= \(\frac{2}{9}\)

Ta có: \(\frac{4}{15}=\frac{4.3}{15.3}=\frac{12}{45};\frac{2}{9}=\frac{2.5}{9.5}=\frac{10}{45}\)

Vì \(\frac{12}{45}>\frac{10}{45}\Rightarrow\frac{4}{15}>\frac{2}{9}\Rightarrow A>B\)

Vậy A > B

\(A=\dfrac{8056}{2012.16-1982}\)

\(A=\dfrac{8056}{32192-1982}\)

\(A=\dfrac{8056}{30210}=\dfrac{12}{45}\)

\(B=\dfrac{1.2.6+2.4.12+4.8.24+7.14.42}{1.6.9+2.12.18+4.24.36+7.42.63}\)

\(B=\dfrac{12+96+768+4116}{54+432+3456+18522}\)

\(B=\dfrac{4992}{22464}=\dfrac{10}{45}\)
Vậy: \(\dfrac{12}{45}>\dfrac{10}{45}\Rightarrow A>B\)

21 trên 4 bạn ạ

Cách giải là gì bn????

a) Ta có: \(\left(-65\right)\cdot\left(87-17\right)-87\cdot\left(17-65\right)\)

\(=-65\cdot87+65\cdot17-87\cdot17+87\cdot65\)

\(=17\left(65-87\right)=17\cdot\left(-22\right)=-374\)

b) Ta có: \(\left(135-35\right)\cdot\left(-37\right)+37\cdot\left(-42-58\right)\)

\(=\left(-100\right)\cdot37+37\cdot\left(-100\right)\)

\(=37\left(-100-100\right)=37\cdot\left(-200\right)=-7400\)

= 65 x ( 121 + 11) - 35 x ( 17 + 115 ) 

= 65 x 132 - 35 x 132 

= ( 65 - 35) x 132 

= 30 x 132 

= 3960

65x121-35x17+11x65-115x35=3.960

\(65\cdot121-35\cdot17+11\cdot65-115\cdot35\)

\(=65\cdot\left(11+121\right)-35\cdot\left(115+17\right)\)

\(=65\cdot132+35\cdot132\)

\(=132\cdot\left(65+35\right)\)

\(=132\cdot100\)

\(=13200\)

a, (135-35).(-37)+37.(-42-58)

= 100.(-37)+37.(-100)

= 100.(-37)+(-37).100

= (-37).(100+100)

= (-37).200

= -7400

b, -65.(87-17)-87.(17-65)

= -65.70-87.(-48)

= -4550+4176

=-374

c, [3.(-2)-(-8)].(-7)-(-2).(-5)

= [(-6)+8].(-7)+(-10)

= 2.(-17)

= -34

Các bạn nhớ ghi cách làm ra nhé!

C

C

C