a: \(\Leftrightarrow\left[\left(3x+14\right):4-3\right]:2=1\)

=>(3x+14):4-3=2

=>(3x+14):4=5

=>3x+14=20

=>3x=6

hay x=2

b: \(\Leftrightarrow\left[\left(x:4+17\right):10+3\cdot16\right]:10=5\)

\(\Leftrightarrow\left(x:4+17\right):10=50-48=2\)

=>x:4+17=20

=>x:4=3

hay x=12

c: \(\Leftrightarrow2\cdot15^2+\left[2\cdot125-\left(2x+4\right)\cdot5\right]:19=453\)

\(\Leftrightarrow250-\left(2x+4\right)\cdot5=\left(453-450\right)\cdot19=57\)

=>5(2x+4)=197

=>2x+4=197/5

=>2x=177/5

hay x=177/10

d: \(\Leftrightarrow\left(19x+50\right):14=5^2-4^2=9\)

=>19x+50=126

=>19x=76

hay x=4

e: \(\Leftrightarrow2\cdot3^x=10\cdot3^{12}+8\cdot3^{12}=18\cdot3^{12}\)

\(\Leftrightarrow3^x=3^2\cdot3^{12}=3^{14}\)

hay x=14

f: \(\Leftrightarrow3\left(x+2\right):7=30\)

=>3(x+2)=210

=>x+2=70

hay x=68

g: \(2480-1570+200-x+5=1010\)

=>1115-x=1010

hay x=105

=10 + 19/10 + 4/15 -1 + 5/15 

= 10 - 1 + 4/15 + 5/15 + 19/10

= 9 + 9/15 + 19/10

= 135/15 + 9/15 + 19/10

= 144/15 + 19/15

=...

\(\dfrac{2}{5}+\dfrac{19}{10}+\dfrac{4}{15}-1+\dfrac{5}{15}\)

\(=\dfrac{2}{5}+\dfrac{4}{15}+\dfrac{5}{15}+\dfrac{9}{10}\)

\(=\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{9}{10}\)

\(=\dfrac{19}{10}\)

\(\left(6,27-1,38\right)\div\left(x\div2\right)=3,26\)

\(4,89\div\left(x\div2\right)=3,26\)

\(x\div2=4,89\div3,26\)

\(x\div2=1,5\)

\(x=1,5\times2\)

\(x=3\)

Chúc bạn hok tốt !

\(\left(6,27-1,38\right):\left(x:2\right)=3,26\)

\(4,89:\left(x:2\right)=3,26\)

\(x:2=4,89-3,26\)

\(x:2=1,63\)

\(x=1,63\times2\)

\(x=3,26\)

Vì AB và DC cùng vuông góc với đường thẳng AD nên AB // DC ( Theo nhận xét trang 48)

=3,26(728+1+270)

=3,26*999=3256,74

\(3,26\cdot728+3,26+3,26\cdot270\)

\(=3,26\cdot\left(728+1+270\right)\)

\(=3,26\cdot999\)

\(=3,26\cdot\left(1000-1\right)\)

\(=3,26\cdot1000-1\cdot3,26\)

\(=3260-3,26\)

\(=3256,74\)

a.Đề bài

=1/2 x 2/3 x 3/4  x...x 9/10

rút gọn

= 1-1/10 
= 9/10

k mình nha học tốt

các bạn giúp mình nhanh nhanh với

1)  A = -1 / 3

2)  B = -35 / 2

  Chúc em làm bài tốt !