a) 2629 x 21 - 2526 = 60570

b) 1575 + 81740 : 268 - 1255 = 625

c) 25 x 69 x 4 = 6900

a) 2629 x 21 - 2526= 52 683

b) 1575 + 81740 : 268-1255 = 1575 + 305-1255= 625

c) 25 x 69 x 4= 6900

tick mn nha

6900 nha

Bài 2: Tính bằng cách thuận tiện nhất

\(\text{a. 1255 + 436 + 145}\)

\(=\left(1255+145\right)+436\)

\(=1400+436\)

\(=1836\)

\(\text{b. 142 x 12 + 142 x 18}\)

\(=142\times\left(12+18\right)\)

\(=142\times30\)

\(=4260\)

\(\text{c. 4 x 18 x 25}\)

\(=\left(25\times4\right)\times18\)

\(=100\times18\)

\(=1800\)

Bài 2:

a: \(=1400+436=1836\)

b: =142(12+18)

=142*30

=4260

c: \(=100\cdot18=1800\)

Bài 3:

a: \(41m^219dm^2>409dm^2\)

b: \(90000cm^2< 90m^2\)

c: \(30m^26dm^2< 3060dm^2\)

d: \(8012cm^2>8dm^212cm^2\)

e: \(5dm^29cm^2=509cm^2\)

f: \(3940dm^2=39m^240dm^2\)

g: \(300m^26dm^2>3006dm^2\)

h: \(2009cm^2< 21dm^2\)

 20 . 2^x + 1 = 10.4^2 + 1 

 20 . 2^x + 1 = 10 . 16 + 1

20 . 2^x + 1 = 161

20 . 2^x = 161 - 1

20 . 2^x = 160

2^x = 8

2^x = 2^3

=> x = 3

Ban co giai dc phan 2 ko ?

( 4 - x : 2 )^3 - 1 = 2 . ( 2^3 - 5 : 2^0 )

( 4 - x : 2 )^3 - 1 = 2 . ( 8 - 5 : 1 )

( 4 - x : 2 )^3 - 1 = 2 . 3

( 4 - x : 2 )^3 - 1 = 6

( 4 - x : 2 )^3  = 7

=> ko tìm đc x

A= 155:5=31

B= 155:5 (Lấy phần nguyên)= 31

C= 155:5 (Lấy số dư) = 0

D=1255:20 (Lấy phần nguyên)= 62

E=1255:20(Lấy số dư) = 15

(nhớ tick nha)

Đặt C(x)=0

\(\Leftrightarrow-2x\left(2x-3\right)-2\left(x-1\right)=0\)

\(\Leftrightarrow-4x^2+6x-2x+2=0\)

\(\Leftrightarrow-4x^2+4x+2=0\)

\(\Leftrightarrow4x^2-4x-2=0\)

\(\Leftrightarrow\left(2x-1\right)^2=3\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=\sqrt{3}\\2x-1=-\sqrt{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=\sqrt{3}+1\\2x=-\sqrt{3}+1\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\sqrt{3}+1}{2}\\x=\dfrac{-\sqrt{3}+1}{2}\end{matrix}\right.\)

Đặt Q(x)=0

\(\Leftrightarrow2\left(x-3\right)-\left(x-1\right)=0\)

\(\Leftrightarrow2x-6-x+1=0\)

\(\Leftrightarrow x=5\)