90 độ<x<180 độ

=>cosx<0

=>\(cosx=-\sqrt{1-\left(\dfrac{12}{13}\right)^2}=-\dfrac{5}{13}\)

\(tanx=\dfrac{12}{13}:\dfrac{-5}{13}=-\dfrac{12}{5}\)

\(E=\dfrac{6\cdot\dfrac{-12}{5}+\dfrac{12}{13}}{2\cdot\dfrac{-5}{13}+\dfrac{5}{12}}=\dfrac{-\dfrac{72}{5}+\dfrac{12}{13}}{-\dfrac{10}{13}+\dfrac{5}{12}}=\dfrac{10512}{275}\)

a) (2⁴⁷ x 5¹⁴ x 2¹³ x 9¹³ x 5¹⁷ x 9¹⁷ ) : (2³⁰ x 2³⁰ x 5³⁰ x 9³⁰)

(2⁶⁰ x 5³¹ x 9³⁰) : (2⁶⁰ x 5³⁰ x 9³⁰) = 5

Vì \(36x^2⋮36\) và \(9864⋮36\)

\(\Rightarrow17y^2⋮36\). Mà \(UCLN\left(36;17\right)=1\) suy ra \(y^2⋮36\)

\(\Rightarrow y⋮6\). Mặt khác \(17y^2< 9864\Rightarrow y^2< 580\Rightarrow y< 24\)

\(\Rightarrow y\in\left\{0;6;12;18\right\}\). Thay vào ta thấy y=18 thỏa mãn suy ra x=11

Vậy x=11;y=18

a,3/5.(5+12+1/3)

=3/5.52/3

=52/5

b,=3/5.5/3.3/4

=1.3/4

=3/4

Anh tính thẳng ra luôn nhé.

a. 3/5 x 5 + 12 x 3/5 + 3 : 5/3 = 12

b. 3/5 x 45/27 x 135/180 = 3/4

a. 3/5 x 5 + 12 x 3/5 + 3 : 5/3

= 3/5 x 5 + 12 x 3/5 + 3 x 3/5

= 3/5 x ( 5 + 15 + 3)

= 3/5 x 20

= 12

b. 3/5 x 45/27 x 135/180

= 3/5 x 5/3 x 3/4

= 1 x 3/4

= 3/4

vì 36x²chia hết cho 36, 9864chia hết cho 36=>17y² chia hết cho 36.Mà ƯCLN(36, 17)=1=>y²chia hết cho 36

=>y chia hết cho 6

mặt khác 17y²<9864=>y²<580=>y<24

=>y là 0 hoặc 6 hoặc 12 hoặc 18

thử từng trường hợp, ta được y=18,x=11

B2:tìm x biết

1)x+18=6-2x

<=> 3x=-12

<=> x= -4

 2)17-x=7-6x

<=>5x=-10

<=>x=-2            

3)x+15=20-4x  

<=>5x=5

<=>x=1

4)7x-4=20+3x                

<=> 4x=24

<=>x=6

5)-12+x=5x-20    

<=>4x=8

<=>x=2

6)4x-18=x+27

<=>3x=45

<=>x=9

7) 2.(x-5)-3.(x+7)=14

<=>2x-10-3x-21=14

<=>-x=14+10+21=45

<=>x=-45

8)5.(x-6)-2.(x+3)=12

<=>5x-30-2x-6=12

<=>3x=48

<=>x=12

9)-7.(5-x)-2.(x-10)=15

<=>-35+7x-2x+20=15

<=>5x=30

<=>x=6

10)3. ( x - 4 ) - ( 8 - x )=12

<=>3x-12-8+x=12

<=>4x=32

<=>x=8

11)4.(x-5)-(x+7)=-19

<=>4x-20-x-7=-19

<=>3x=8

<=>x=8/3

 12)7.(x-3)-5.(3-x)=11x-5

<=>7x-21-15+5x=11x-5

<=>x=31

b1:bỏ ngoặc rồi tinh hợp lí

1) -( -66)+34+(-73)-27+99=66+34-73-27+99 =100-100+99=99

2)54-(45-30+54)-30+5=54-45+30-54-30+5=-45+5=-40     

3)42-56+33-(33-56+42)=42-56+33-33+56-42=0

4)50-(47+50-18)+(47-18)=50-47-50+18+47-18=0      

5) |25-24-10|-(28-30+4)=9-28+30-4=39-32=7

6)-(-73)+(44-94+27)+94=73+44-94+27+94=100+44=144

7) (-33+180-75)-(180+25)=-33+180-75-180-25=-100-33=-133

8)120-(-92+120-18)-92=120+92-120+18=108

b1:bỏ ngoặc rồi tinh hợp lí 

1) -( -66)+34+(-73)-27+99=66+34-73-27+99 =100-100+99=99 

2)54-(45-30+54)-30+5=54-45+30-54-30+5=-45+5=-40 

3)42-56+33-(33-56+42)=42-56+33-33+56-42=0

4)50-(47+50-18)+(47-18)=50-47-50+18+47-18=0 

5) |25-24-10|-(28-30+4)=9-28+30-4=39-32=7 

6)-(-73)+(44-94+27)+94=73+44-94+27+94=100+44=144 

7) (-33+180-75)-(180+25)=-33+180-75-180-25=-100-33=-133 

8)120-(-92+120-18)-92=120+92-120+18=108

a) x - 7 = 5. 0 => x - 7 = 0 =>x = 7.

b) x: 3 = 47 +13 => x: 3 = 60 => x = 60.3 => x = 180.

c) x :  7 - 7 = 0 hoặc x : 12 - 12 = 0. Do đó x = 49 hoặc x = 144.

d) x : 2 = 150 - 135 => x: 2 = 15 => x = 15.2 => x = 30.

e) 100: x = 140 -120 => 100: x = 20 => x = 100:20 => x = 5.

g) x : 5 = 300 - 273 => x : 5 = 27 =>x = 27.5 => x = 135

a) x - 7 = 5. 0 => x - 7 = 0 =>x = 7.

b) x: 3 = 47 +13 => x: 3 = 60 => x = 60.3 => x = 180.

c) x :  7 - 7 = 0 hoặc x : 12 - 12 = 0. Do đó x = 49 hoặc x = 144.

d) x : 2 = 150 - 135 => x: 2 = 15 => x = 15.2 => x = 30.

e) 100: x = 140 -120 => 100: x = 20 => x = 100:20 => x = 5.

g) x : 5 = 300 - 273 => x : 5 = 27 =>x = 27.5 => x = 135