Question

[linlingg103]

mn lm giúp mk mí bài này vs!!!

Bài 1: Tính bỉu thức:

1, 90 - (2² . 25 - 3² . 7)

2, 720 - {40 . [(120 - 70) : 25 + 2³]}

Bài 2: Tìm x:

a. 5x - 17 = 38

b. 2x - 138 = 2³ . 3²

c. 7x - 3³ = 2⁷ : 2⁴

d. (81 - x) - 32 = 19

e. 36 + (x - 19) = 54

f. 45 + (x - 6) . 3 = 60

g. 100 - 7 . (x - 5) = 58

h. |x| - 5 = 3

i. |x - 5| = 7

Answer 1

[Thanh Trà]

Bài 1:

1,\(90-\left(2^2.2^5-3^2.7\right)\)

\(=90-\left(2^7-9.7\right)\)

\(=90-\left(128-63\right)\)

\(=25\)

2,\(720-\left\{40.\left[\left(120-70\right):25+2^3\right]\right\}\)

\(=720-\left(40.1258\right)\)

\(=-49600\)

Bài 2:

a,\(5x-17=38\)

\(5x=55\)

\(x=11\)

b,\(2x-138=2^3.3^2\)

\(2x-138=72\)

\(2x=210\)

\(x=105\)

c,\(7x-3^3=2^7:2^4\)

\(7x-27=8\)

\(7x=35\)

\(x=5\)

d,\(\left(81-x\right)-32=19\)

\(\left(81-x\right)=51\)

\(x=30\)

e,\(36+\left(x-19\right)=54\)

\(x-19=18\)

\(x=37\)

f,\(45+\left(x-6\right).3=60\)

\(\left(x-6\right).3=15\)

\(x-6=5\)

\(x=11\)

g,\(100-7.\left(x-5\right)=58\)

\(7\left(x-5\right)=42\)

\(x-5=6\)

\(x=11\)

h,\(\left|x\right|-5=3\)

\(\left|x\right|=8\)

\(\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-8\end{matrix}\right.\)

Vậy...

i,\(\left|x-5\right|=7\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=7\\x-5=-7\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-2\end{matrix}\right.\)

Vậy...