72 . 56 - 12 . 44 + 72 . 44 - 12 . 5

=72 x (56 + 44) + 12 x (44 + 56)

= 72 x 100 + 12 x 100

= 7200 + 1200

= 8400

a) \(56^2+44^2+2.56.44=56^2+2.56.44+44^2=\left(56+44\right)^2=100^2=10000\)

b) \(36^2+64^2+72.64=36^2+2.36.64+64^2=\left(36+64\right)^2=100^2=10000\)

c) \(136^2+36^2-72.136=136^2-2.36.136+36^2=\left(136-36\right)^2=100^2=10000\)

a) $56^2+44^2+2.56.44=56^2+2.56.44+44^2=\left(56+44\right)^2=100^2=10000$562+442+2.56.44=562+2.56.44+442=(56+44)2=1002=10000

b) $36^2+64^2+72.64=36^2+2.36.64+64^2=\left(36+64\right)^2=100^2=10000$362+642+72.64=362+2.36.64+642=(36+64)2=1002=10000

c) $136^2+36^2-72.136=136^2-2.36.136+36^2=\left(136-36\right)^2=100^2=10000$

112

112

112

a) \(21^{15}=21^{3.5}=\left(21^3\right)^5=9261^5\)

Vì \(9261>27\Rightarrow9261^5>27^5\Rightarrow21^{15}>27^5\)

b) \(15^{12}=\left(3.5\right)^{12}=3^{12}.5^{12}\)

\(81^3.125^5=\left(3^4\right)^3.\left(5^3\right)^5=3^{4.3}.5^{3.5}=3^{12}.5^{15}\)

Vì \(3^{12}=3^{12}\)mà \(5^{12}< 5^{15}\Rightarrow3^{12}.5^{12}< 3^{12}.5^{15}\Rightarrow15^{12}< 81^3.125^5\)

C

C

c

em lớp 6  nha

B= 1/2 + 1/6 + 1/12 +1/20 + 1/30 + 1/42 + 1/56 + 1/72

B= 1/1*2 + 1/2*3 + 1/3*4 + 1/4*5 + 1/5*6 + 1/6*7 + 1/7*8 + 1/8*9

B=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9

B=1+0-0-0-0-0-0-0-1/9

B=1-1/9

B=8/9

k em nha

phần A em chịu

còn câu dưới đó e

ai giải cho tui đi

\(888-\left(-333\right)-222+70\)

\(=888+\left(333-222\right)+70\)

\(=888+111+70\)

\(=999+70\)

\(=1069\)

\(-97-15+44-35-12+56\)

\(=\left(-97-15-35-12\right)+\left(44+56\right)\)

\(=-159+100\)

\(=-59\)

thanks

[44-(56-x)].12=384

44-(56-x)=32

56-x=12

x=44

[44- (56-x) ] . 12 = 384

<=> (44-56+x) . 12 = 384

<=> (-12 + x) . 12  = 384

<=> 12x - 144       = 384

<=> 12x               = 384 + 144

<=> 12x               = 528

<=>    x                = 528 : 12

<=>    x                = 44

Vậy x = 44

[44-(56-x)]=384:12=32

       56-x  =44-32=12

            x  =56-12=44

500 nha

1+88+99+12+33+67+44+56+100

=(1+99)+(88+12)+(33+67)+(44+56)+100

=100+100+100+100+100

=100x5

=500

500 nha