trl : -6009592963586304

HT~

A, 34x77+286x74-209x74                     B, 58x75+50x58-58x25                        C, 123x101                      D, 169x11                  E, 99x34

=34x77+[286x(74-74)]                              =58x(75+50-25)                                     =12423                            =1859                      =3366

=34x77+(286x0)                                       =58x100

=2618+0                                                   =5800

=2618

\(\frac{45.86+45.15-45}{50.37-50.5+50.58}\)

\(=\frac{45.\left(86+15-1\right)}{50.\left(37-5+58\right)}\)

\(=\frac{45.100}{50.90}\)

\(=1\)

học tốt

A = \(\frac{45x\left(86+15-1\right)}{50x\left(37-5+58\right)}\)

A=\(\frac{45x100}{50x90}\)= \(\frac{2}{2}\)= 1

(Cái phần cuối thì bạn rút họn 45 với 90, 50 với 100)

\(A=\frac{45\times86+45\times15-45}{50\times37-50\times5+50\times58}=\frac{45\times\left(86+15-1\right)}{50\times\left(37-5+58\right)}=\frac{45\times100}{50\times90}\)

                           \(=\frac{5\times9\times10\times10}{5\times10\times9\times10}=1\)

Vậy A = 1

99x34+25x2=100x34-34+50=3400+(50-34)=3400+16=3416

99* 34+ 25* 2= 3366 + 50= 3416

\(99.34+25.2=3366+50=3416\)

\(58x75+58x50-58x25\)

\(=58x\left(75+50-25\right)\){Theo tính chất kết hợp}

\(=58x100=5800\)

58x75+58x50-58x25 = 58 x ( 75 + 50 - 25 ) = 58 x 100 = 5800

=5800

=58.(75+50-25)

=58.120

=6960

sửa lại

=58.100

=5800

=  225.55 +  225.55

=  451.1 

a)\(65.3,47+3,47.65\)
\(=65.\left(3,47+3,47\right)\)
\(=65.6,94\)
\(=451,1\)

\(65\times\left(3,47+3,47\right)=65\times6,94=451,1\)

a: \(78\cdot82=80^2-4=6400-4=6396\)

b: \(45^2+90\cdot55+55^2=100^2=10000\)

`30 xx 25 xx 7 xx8`

`=(30 xx7) xx (25xx8)`

`=210 xx200`

`=42000`

`----`

`75 xx 8 xx 12 xx 14`

`=(75xx8) xx(12xx14)`

`=600xx168`

`=100800`

\(a.30\times25\times7\times8=\left(30\times7\right)\times\left(25\times8\right)=210\times200=42000\)

\(b.75\times8\times12\times14=\left(75\times12\right)\times\left(8\times14\right)=900\times112=100800\)

\(a,30.25.7.8\\ =\left(30.7\right).\left(25.8\right)\\ =210.200\\ =42000\\ b,75.8.12.14\\ =\left(75.12\right).\left(8.14\right)\\ =900.112\\ =100800\)