cứu tui 

Ta có:\(2^{30}=\left(2^3\right)^{10}=8^{10}< 9^{10}=\left(3^2\right)^{10}=3^{20}\)

\(3^{30}=3^{20}.3^{10}< 3^{20}.4^{10}=3^{20}.\left(2^2\right)^{10}=3^{20}.2^{20}=\left(3.2\right)^{20}=6^{20}\)

\(4^{30}=4^{20}.4^{10}=4^{20}.\left(2^2\right)^{10}=4^{20}.2^{20}=\left(4.2\right)^{20}=8^{20}\)

nên \(2^{30}+3^{30}+4^{30}< 3^{20}+6^{20}+8^{20}\)

a) 86 – 16 = 70 

b) 23 x 2 – 1 = 23 

c) 250 : 5 + 5 = 25 

d) 40 + 80 : 4 = 30 

e) 80 + 4 : 2 = 42 

f) 70 + 30 : 2 = 50 

g) 90 + 30 x 3 = 180 

h) 70 + 30 : 2 = 85 

Bài 3:

a: \(S=1+5^2+5^4+\cdots+5^{200}\)

=>25S=\(5^2+5^4+5^6+\cdots+5^{202}\)

=>25S-S=\(5^2+5^4+\cdots+5^{202}-1-5^2-\cdots-5^{200}\)

=>24S=\(5^{202}-1\)

=>\(S=\frac{5^{202}-1}{24}\)

b: \(4^{30}=\left(2^2\right)^{30}=2^{60}=2^{30}\cdot2^{30}=8^{10}\cdot4^{15}\)

\(3\cdot24^{10}=3\cdot3^{10}\cdot8^{10}=8^{10}\cdot3^{11}\)

mà \(4^{15}>3^{11}\)

nên \(4^{30}>3\cdot24^{10}\)

=>\(2^{30}+3^{30}+4^{30}>3\cdot24^{10}\)

Bài 2:

a: |2x-3|>5

=>\(\left[\begin{array}{l}2x-3>5\\ 2x-3<-5\end{array}\right.\Rightarrow\left[\begin{array}{l}2x>8\\ 2x<-2\end{array}\right.\Rightarrow\left[\begin{array}{l}x>4\\ x<-1\end{array}\right.\)

c: |3x-1|<=7

=>-7<=3x-1<=7

=>-6<=3x<=8

=>\(-2\le x\le\frac83\)

d: \(\left|3x-5\right|+\left|2x+3\right|=7\) (1)

TH1: \(x<-\frac32\)

=>2x+3<0; 3x-5<0

(1) sẽ trở thành: -2x-3-3x+5=7

=>-5x+2=7

=>-5x=5

=>x=-1(loại)

TH2: -3/2<=x<5/3

=>2x+3>=0; 3x-5<0

(1) sẽ trở thành: 2x+3-3x+5=7

=>-x+8=7

=>-x=-1

=>x=-1(nhận)

TH3: x>=5/3

=>2x+3>0; 3x-5>=0

(1) sẽ trở thành: 2x+3+3x-5=7

=>5x-2=7

=>5x=9

=>x=9/5(nhận)

5 x 6 = 30       2 x 6 = 12        3 x 6 = 18        4 x 6 = 24

6 x 5 = 30       6 x 2 = 12        6 x 3 = 18        6 x 4 = 24

Tính nhẩm:

5 x 6 = 30       2 x 6 = 12        3 x 6 = 18        4 x 6 = 24

6 x 5 = 30       6 x 2 = 12        6 x 3 = 18        6 x 4 = 24

30 : 6 = 5       12 : 6 = 2         18 : 6 = 3         24 : 6 = 4

30 : 5 = 6       12 : 2 = 6         18 : 3 = 6         24 : 4 = 6

Học tốt <3

a) 2x-30=-14

2x=(-14)+30

2x=16

x=16:2

x=8

b) 230-4*(x+5)=30

4*(x+5)=230-30

4*(x+5)=200

x+5=200:4

x+5= 50

x=50-5

x=45

\(2^{30}< 24^{30}\)

\(3^{30}< 24^{30}\)

\(4^{30}< 24^{30}\)

\(\Rightarrow2^{30}+3^{30}+4^{30}< 24^{30}+24^{30}+24^{30}\)

\(\Rightarrow2^{30}+3^{30}+4^{30}< 3.24^{30}\)

a) 87 + 92 – 32 = 179 – 32

                   = 147

b) 138 – 30 – 8 = 108 - 8

                  = 100

c) 30 x 2 : 3 = 60 : 3

                  = 20

d) 80 : 2 x 4 = 40 x 4

                  = 160

x>y

k cho mình nha