=  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`

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

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

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

=8,95*90+89,5

=89,5(9+1)

=895

(-0,4)x(-0,5)x(-0,8)

= 0,2x(-0,8)

=-0,16 

3,4x(-23,68)-3,4x45,12+(-31,2)x3,4

=34,5x5,789+4,211x34,5
=34,5x(5,789+4,211)
=34,5x10
=345

a: \(68^2+64\cdot68+32^2\)

\(=\left(68+32\right)^2\)

=10000

b: \(51\cdot49=50^2-1=2499\)

a: \(20,11\cdot7,5+20,11+20,11+20,11\cdot0,5\)

\(=20,11\left(7,5+1+1+0,5\right)\)

\(=20,11\cdot10=201,1\)

b: \(2,5\cdot12,85\cdot4\)

\(=12,85\cdot\left(2,5\cdot4\right)\)

\(=12,85\cdot10=128,5\)

a: 

b: 

a: 

b: 

=72x100=7200

=72x100=7200

\(=-375\left(69+31\right)=-375\cdot100=-37500\)