. là dấu nhân hay dấu phẩy vậy bạn

b)[1,1*(-4,3+4,5)]:(-10+10,01)

(1,1*0,2):0,01

=0,22:0,01

=22

c)=(6,7+5,66-3,7+4,34)*(-76,6*1,2+7,66*10*1,2)

=(6,7+5,66-3,7+4,34)*(-76,6*1,2+76,6*1.2)

=(6,7+5,66-3,7+4,34)*[1,2*(-76,6+76,6)]

=(6,7+5,66-3,7+4,34)*(1,2*0)

=(6,7+5,66-3,7+4,34)*0

=0

\(a.\)

\(6,5+1,2+3,5-5,2+6,5-4,8\)

\(=\left(-5,2+1,2\right)+\left(3,5+6,5\right)+\left(6,5-4,8\right)\)

\(=\left(-4\right)+10+1,7\)

\(=6+1,7\)

\(=7,7\)

\(b.\)

\(\left(-4,3.1,1+1,1.4,5\right):\left(-0,5:0,05+10,01\right)\)

\(=\left[1,1.\left(-4,3+4,5\right)\right]:\left(-10+10.01\right)\)

\(=\left[1,1.0,2\right]:\left(0,01\right)\)

\(=0,22:0,01\)

\(=22\)

\(c.\)

\(\left(6,7+5,66-3,7+4,34\right).\left(-76,6.1,2+7,66.12\right)\)

\(=\left(6,7+5,66-3,7+4,34\right).\left[76,6\left(-1,2\right)+7,66.12\right]\)

\(=13.0\)

\(=0\)

a)
\(\frac{1\cdot2+2\cdot4+3\cdot6+4\cdot8+5\cdot10}{3\cdot4+6\cdot8+9\cdot12+12\cdot16+15\cdot20}\)

\(=\frac{1\cdot2\cdot\left(1+2\cdot2+3\cdot3+4\cdot4+5\cdot5\right)}{3\cdot4\cdot\left(1+2\cdot2+3\cdot3+4\cdot4+5\cdot5\right)}\)

\(=\frac{1\cdot2}{3\cdot4}=\frac{1}{6}\)

b) \(\frac{12\cdot13+24\cdot26+36\cdot39}{24\cdot26+48\cdot52+72\cdot78}\)

\(=\frac{12\cdot13\cdot\left(1+2\cdot2+3\cdot3\right)}{24\cdot26\cdot\left(1+2\cdot2+3\cdot3\right)}\)

\(=\frac{12\cdot13}{24\cdot26}=\frac{1}{4}\)

\(\frac{2\cdot3+4\cdot6+14\cdot21}{3\cdot5+6\cdot10+21\cdot35}=\frac{2\cdot3\cdot\left(1+2\cdot2+7\cdot7\right)}{3\cdot5\cdot\left(1+2\cdot2+7\cdot7\right)}=\frac{2\cdot3}{3\cdot5}=\frac{2}{5}\)

19.56 - 4.8 : 1.2 x 1.8

= 1064 - 32 : 2 x 8

= 1064 - 16 x 8

= 1064 - 128

= 936

19 . 56 -  4.8 : 1 . 2 x 1. 8

=19 . 56 -  4 x 1.8

=19 . 56 - 7.2

=12 . 36

Chúc bạn hk tôt!

@ミ★Đờĭღ๖ۣۜTɦĭếυ★彡 ơi bạn tính j lạ vậy???

\(\dfrac{1.2+2.4+3.6+4.8+5.10}{3.4+6.8+9.12+12.16+15.20}\)

\(=\dfrac{1.2+2.4+3.6+4.8+5.10}{3.4+3.4.2.2+3.4.3.3+3.4.2.8+3.4.5.5}\)

\(=\dfrac{1.2.\left(4+3^2+2.8+5^2\right)}{3.4.\left(4+3^2+2.8+5^2\right)}\)

\(=\dfrac{1}{6}\)

\(\dfrac{1.2+2.4+3.6+4.8+5.10}{3.4+6.8+9.12+12.16+15.20}\)

\(=\dfrac{1.2+1.2.2^2+1.2.3^2+1.2.4^2+1.2.5^2}{3.4+3.4.2^2+3.4.3^2+3.4.4^2+3.4.5^2}\)

\(=\dfrac{1.2\left(1+2^2+3^2+4^2+5^2\right)}{3.4\left(1+2^2+3^2+4^2+5^2\right)}\\ =\dfrac{2}{12}=\dfrac{1}{6}\)

\(\dfrac{1.2+2.4+3.6+4.8+5.10}{3.4+6.8+9.12+12.16+15.20}\)

= \(\dfrac{2\left(1+4+9+16+25\right)}{4\left(3+12+27+48+65\right)}\)

= \(\dfrac{2.55}{4.155}\)

= \(\dfrac{1.55}{2.155}\)

= \(\dfrac{55}{310}=\dfrac{11}{62}\)

Câu 1 : \(0,36\times630+0,6\times36\times6+3,6\)

\(=0,36\times10\times63+0,6\times6\times36+3,6\)

\(=3,6\times63+3,6\times36+3,6\)

\(=3,6\times\left(63+36+1\right)\)

\(=3,6\times100\)

\(=360\)

 Câu 2 :\(3,5\times20,2+6,5\times27,9+3,5\times2,2-6,5\times5,5\)

\(=3,5\times\left(20,2+2,2\right)+6,5\times\left(27,9-5,5\right)\)

\(=3,5\times22,4+6,5\times22,4\)

\(=22,4\times\left(3,5+6,5\right)\)

\(=22,4\times10\)

\(=224\)