a-b=-4

\(\Rightarrow\)2a-2b=-8

\(\Rightarrow\)a+2b+2a-2b=11-8

\(\Rightarrow\)3a=3

\(\Rightarrow\)a=1

\(\Rightarrow\)b=a+4=1+4=5

\(\Rightarrow\)4a-b=1.4-5=4-5=-1

a) 3x (12x - 4) - 9x (4x - 3) = 30

\(\Leftrightarrow\)36x²  – 12x – 36x²  + 27x = 30

\(\Leftrightarrow\)15x = 30

\(\Leftrightarrow\)x = 2

b) x (5 - 2x) + 2x (x - 1) = 15

\(\Leftrightarrow\)5x – 2x^​2  + 2x²  – 2x = 15

\(\Leftrightarrow\)3x = 15

\(\Leftrightarrow\)x =5

1+2+3+4+5+6+7+8

=(2+8)+(3+7)+(4+6)+1+5

=10+10+10+6

=10.3+6

=30+6

=36

So the answer is 36

1+2+3+4+5+6+7+8

=(2+8)+(3+7)+(4+6)+1+5

\(\dfrac{3}{m}=\dfrac{27}{72}\\\Leftrightarrow \dfrac{3.9}{9m}=\dfrac{27}{72}\\\Leftrightarrow \dfrac{27}{9m}=\dfrac{27}{72}\\ \Rightarrow9m=72\\ \Rightarrow m=8\)

23 rows of 27 chairs each

So 23.27=621 (chairs)

So there are 621 chairs in the room

The absolute difference between the length and width of rectangle MNOP​ is |(4x+9)-(4x-3)|

=|4x+9-4x+3|

=|12|

=12

So the answer is 12

2011^x=x²⁰¹¹

So 2011²⁰¹¹=x^​x

So x=2011

2^x+2^y+2^​z=1024

^​but 1024=512+256+256

so \(\left[{}\begin{matrix}\left\{{}\begin{matrix}x=9\\y=8\\z=8\end{matrix}\right.\\\left\{{}\begin{matrix}x=8\\y=9\\z=8\end{matrix}\right.\\\left\{{}\begin{matrix}x=8\\y=8\\z=9\end{matrix}\right.\end{matrix}\right.\)

x^​2​+x+1\(\ne\)0 with any value of x

So don't have any value of x satisfy

So don't have any value of A

So A\(\in\)\(\varnothing\)

1+2+3+10000000

=(1+2+3)+10000000

=6+10000000

=10000006

10+20+30+40+50+60+70+80+90

=(10+90)+(20+80)+(30+70)+(40+60)+50

=100+100+100+100+50

=100.4+50

=400+50

=450

x:3:2=9

\(\Leftrightarrow x=9.2.3\)

\(\Leftrightarrow x=54\)

So the answer is 54

S dodecagon = S original rectangle - S removed squares

S original rectangle = 4.5=20 (cm²)

S removed squares = 1².4=4 (cm​²)

So S dodecagon = 20-4=16 (cm²)

20+30+40+50+60+70

=(20+30+50)+(40+60)+70

=100+100+70

=100.2+70

=200+70

=270

So the answer is 270

=(1+9)+(2+8)+(3+7)+(4+6)+10+5

=10+10+10+10+10+5

=10.5+5

=50+5

=55

So the answer is 55

99999.55555

=(100000-1).55555

=5555500000-55555

=5555444445

40%\(\times\dfrac{1}{3}\times24\div0,8\)

=\(\dfrac{40.1.24}{100.3}\div\dfrac{4}{5}\)

=\(\dfrac{16}{5}.\dfrac{5}{4}\)

= 4

So the answer is 4

we have : 0,0A=\(\sqrt{0,0049}\)

but \(\sqrt{0,0049}=0,07\)

\(\Rightarrow0,0A=0,07\)

\(\Rightarrow A=7\)

So the value of A is 7

a,x=100-33=67

b,x=100-88=12

c,x=100-22=78

d,x=100-18=82

The edge of the cube is 2cm

\(\Rightarrow\) The volume is : 2.2.2=8 (cm²)

So the volume of the cube is 8cm²

The edge of square is 9cm

\(\Rightarrow\) The area : 9.9=81 (cm^​2)

So the area is 81 cm^​2

1200.

300.

150.

\(\Rightarrow x=\dfrac{2}{7}+\dfrac{2}{5}\)

\(\Rightarrow x=\dfrac{10}{35}+\dfrac{14}{35}\)

\(\Rightarrow x=\dfrac{10+14}{35}\)

\(\Rightarrow x=\dfrac{24}{35}\)

Quick Count:

75+25+13+91+87+52+48+9+?

Ai tk mk thì sẽ mk tk lại

30.40

=3.10.4.10

=(3.4).(10.10)

=12.100

=1200

So the answer is 1200

|1,18-2,36|

= |2,36-1,18|

= |1,18|

= 1,18

So the absolute difference is 1,18

As off topic we have :

5x+10y\(-5x-2y=80-48\)

\(\Rightarrow8y=32\)

\(\Rightarrow y=4\)

And x-2y=0

So x = 8

So \(\left\{{}\begin{matrix}x=8\\y=4\end{matrix}\right.\)

We have 100 = 25.4

So the fraction is \(\dfrac{25}{100}=\dfrac{1}{4}\)

There are 6 unit squares is shaded of 20 unit spuares

So fractional part is \(\dfrac{6}{20}=\dfrac{3}{10}\)

A year has 12 months

\(\Rightarrow\) 35 years has : 12.35=420 (months)

So there are 420 months in 35 years

75+75.3

= 75.(1+3)

= 75.4

= 300

20+30+40+50+60+70+80

= (20+80)+(30+70)+(40+60)+50

= 100+100+100+50

+350

If A=2

\(\Rightarrow n^{2011}.\left(n+1\right)=1\\ \Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}n^{2011}=-1\\n+1=1\end{matrix}\right.\\\left\{{}\begin{matrix}n^{2011=1}\\n+1=-1\end{matrix}\right.\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}n=-1\\n=0\end{matrix}\right.\left(loại\right)}\\\left\{{}\begin{matrix}n=1\\n=-2\end{matrix}\right.\left(loại\right)\end{matrix}\right.\)​If A > 2

\(\Rightarrow n^{2011}.\left(n+1\right)=2k\left(k\in N\cdot\right)\)

Xét n lẻ\(\Rightarrow n+1chẵn\)

Xét n chẵn \(\Rightarrow n^{2011}chẵn\)

Vậy với mọi n thì A là số nguyên tố

Biết đéo đúng vẫn đăng :v

\(\dfrac{2^{10}.5^6.30^5}{4^2.5^9.60^2}=\dfrac{2^{10}.5^6.30^5}{2^2.2^2.5^9.30^2.2^2}=\dfrac{2^4.30^3}{5^3}=\dfrac{2^4.5^3.6^3}{5^3}=2^4.6^3=16.216=3456\)

78 > x > 56

so x \(\in\)\(\left\{57;58;59;60;61;62;63;64;65;66;67;68;69;70;71;72;73;74;75;76;77\right\}\)

because 77 > ... >57

so the x's bigger valte is 77