hk hừng đẳng thưc chưa

chưa bn

(3x-2)^2=(2-3x)^4

(3x-2)(3x-2)=(2-3x)^4

-(2-3x)x-(2-3x)=(2-3x)(2-3x)(2-3x)(2-3x)

0=(2-3x)^2

0=2-3x

x=3/2

hok tôt

A=1+3+3^2+3^3+3^4+3^5+3^6

3A=3+3^2+3^3+3^4+3^5+3^6+3^7

3A-A=(3+3^2+3^3+3^4+3^5+3^6+3^7)-(1+3+3^2+3^3+3^4+3^5+3^6)

A=3^7-1

Vì A =3^7-1 ; B =3^7-1

=> A=B

Sửa đề:

\(A=1+3+3^2+3^3+3^4+3^5+3^6\)

\(3A=3+3^2+...+3^7\)

\(3A-A=\left(3+3^2+3^3+...+3^7\right)-\left(1+3+3^2+...+3^6\right)\)

\(2A=3^7-1\)

\(\Rightarrow A=\frac{3^7-1}{2}< 3^7-1=B\)

Vậy \(A< B\)

Ta có :

\(A=1+3+3^2+3^3+3^4+3^5+3^6\)

\(\Rightarrow3A=3+3^2+3^3+3^4+3^5+3^6+3^7\)

\(\Rightarrow3A-A=\left(3+3^2+3^3+3^4+3^5+3^6+3^7\right)-\left(1+3+3^2+3^3+3^4+3^5+3^6\right)\)

\(\Rightarrow2A=3^7-1\)

\(\Rightarrow A=\frac{3^7-1}{2}< 3^7-1=B\)

Vậy A < B

_Chúc bạn học tốt_

S = 1 + 2 + 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷

= (1 + 2) + (2² + 2³) + (2⁴ + 2⁵) + (2⁶ + 2⁷)

= (1 + 2) + 2²(1 + 2) + 2⁴(1 + 2) + 2⁶(1 + 2)

= (1 + 2)(1 + 2² + 2⁴ + 2⁶) 

= 3(1 + 2² + 2⁴ + 2⁶) \(⋮3\)(ĐPCM)

2S = 1 + 2 + 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ 

S = (1+2 ) + (2² + 2³ ) + (2⁴ + 2⁵ ) + (2⁶ +2⁷)

S = 3 + 2²(1+2) + 2⁴(1+2) + 2⁶(1+2)

S = 3+2².3 + 2⁴.3 + 2⁶ .3 

S = 3(1+2² + 2⁴ + 2⁶ ) \(⋮\) 3

=> đpcm

Vì 1+2=3 \(⋮\)3 =>(1+2)+2²+2³+2⁴+2⁵+2⁶+2⁷=>S \(⋮\)3

Vậy S \(⋮\)9

Nhớ k cho mình nhé !

a) \(x-2=-6\)

\(x=-6+2\)

\(x=-4\)

b) \(15-\left(x-7\right)=-21\)

\(x-7=36\)

\(x=43\)

c) \(4.\left(3x-4\right)-2=18\)

\(4\left(3x-4\right)=20\)

\(3x-4=5\)

\(3x=9\)

\(x=3\)

d) \(\left(3x-6\right)+3=32\)

\(3x-6=29\)

\(3x=29+6\)

\(3x=35\)

\(x=\frac{35}{3}\)

e) \(\left(3x-6\right).3=32\)

\(3x-6=\frac{32}{3}\)

\(3x=\frac{32}{3}+6\)

\(3x=\frac{50}{3}\)

\(x=\frac{50}{9}\)

f) \(\left(3x-6\right):3=32\)

\(3x-6=96\)

\(3x=102\)

\(x=34\)

g) \(\left(3x-6\right)-3=32\)

\(3x-6=35\)

\(3x=41\)

\(x=\frac{41}{3}\)

h) \(\left(3x-2^4\right).7^3=2.7^4\)

\(\left(3x-2^4\right)=2.7=14\)

\(\left(3x-16\right)=14\)

\(3x=14+16=30\)

\(x=10\)

i) \(\left|x\right|=\left|-7\right|\)

\(\left|x\right|=7\)

\(\Rightarrow\orbr{\begin{cases}x=7\\x=-7\end{cases}}\)

k) \(\left|x+1\right|=2\)

\(\Rightarrow\orbr{\begin{cases}x+1=2\\x+1=-2\end{cases}\Rightarrow\orbr{\begin{cases}x=1\\x=-3\end{cases}}}\)

l) \(\left|x-2\right|=3\)

\(\Rightarrow\orbr{\begin{cases}x-2=3\\x-2=-3\end{cases}\Rightarrow\orbr{\begin{cases}x=5\\x=-1\end{cases}}}\)

m) \(x+\left|-2\right|=0\)

\(x+2=0\)

\(x=-2\)

o) \(72-3\left|x+1\right|=9\)

\(3\left|x-1\right|=63\)

\(\left|x-1\right|=21\)

\(\Rightarrow\orbr{\begin{cases}x-1=21\\x-1=-21\end{cases}\Rightarrow\orbr{\begin{cases}x=22\\x=-20\end{cases}}}\)

p) Ta có: \(\left|x-1\right|=3\)

\(\Rightarrow\orbr{\begin{cases}x-1=3\\x-1=-3\end{cases}}\)

mà \(x+1< 0\)

\(\Rightarrow x-1=-3\)

\(\Rightarrow x=-2\)

q) \(\left(x-2\right)\left(x+4\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-2=0\\x+4=0\end{cases}\Rightarrow\orbr{\begin{cases}x=2\\x=-4\end{cases}}}\)

hok tốt!!

A=2+2²+2³+2⁴+2⁵+2⁶

=2.(1+2+2²+2³+2⁴+2⁵)

=2.(1+2+4+8+16+32)

=2.63

=2.7.9 chia hết cho 9(vì trong tích có 1 thừa số là 9)

Chúc bạn học giỏi nha!!!

K cho mik vs nhé Mai Phước Trí

    (-5).7.(-12).|-4|.(-8)

= -35.(-12).4.(-8)

=420.4.(-8)

=1680.(-8)

=-13440

1/ (-5).7.(-12).|-4|.(-8) = -13440

2/ x-(-19)+(-2)mũ 5=14-(-2)mũ 4 => x=(-7)

3/ x+4y-xy =15; không có x;y thỏa mãn đề bài, nếu 3x+4y-xy =16 thì x=8;y=2

a: Ta có: \(3x\left(3x-1\right)-\left(3x+1\right)\left(3x-1\right)=0\)

\(\Leftrightarrow9x^2-3x-9x^2+1=0\)

\(\Leftrightarrow3x=1\)

hay \(x=\dfrac{1}{3}\)

b: Ta có: \(x^2-5x+25-5x=0\)

\(\Leftrightarrow\left(x-5\right)^2=0\)

\(\Leftrightarrow x-5=0\)

hay x=5

\(\left(3x+4\right)^2-\left(3x-1\right)\left(3x+1\right)=9x^2+24x+16-9x^2+1=24x+17\)

Đặt \(24x+17=0\Leftrightarrow x=-\frac{17}{24}\)

đặt 3^x ra ngoài bạn nhé bàn phím mik hỏng rồi ;-;

$\Rightarrow 3^x(1+3+3^2+3^3)=1080$

$\Rightarrow 3^x.40=1080$

$\Rightarrow 3^x=27=3^3$

$\Rightarrow x=3$

\(3^x+3^{x+1}+3^{x+2}+3^{x+3}=1080\)

\(\Rightarrow3^x+3^x.3^1+3^x.3^2+3^x.3^3=1080\)

\(3^x.\left(1+3+9+27\right)=1080\)

\(3^x.40=1080\)

\(3^x=27\)

\(3^x=3^3\)

Vậy: x = 3