Vì \(90^o< x< 180^o\Rightarrow\cos x< 0\)

Có: \(\sin^2x+\cos^2x=1\Leftrightarrow\left(\dfrac{2}{5}\right)^2+\cos^2x=1\Leftrightarrow\cos^2x=\dfrac{21}{25}\Leftrightarrow\cos x=-\dfrac{\sqrt{21}}{5}\left(vì\cos x< 0\right)\)

a: M(x)+N(x)=7x^3-8x^2-13x-7

b: M(x)+Q(x)=12x^3-2x^2-5x-20

c: N(x)+Q(x)=13x^3-22x-9

d: N(x)-Q(x)=-5x^3-6x^2-8x+13

e: Q(x)-M(x)=6x^3+8x^2-9x-2

Ta có : (x - 1)(x + 1)(x + 2)

= (x² - 1) (x + 2)

= x³ + 2x² - x - 2 

Ta có : ( x - 1 ) ( x + 1 ) ( x + 2 )

= ( x^2 - 1 ) ( x + 2 )

= x^3 + 2x^2 - x + 1

= x^3 + 2x^2 - x + 1

\(h=\dfrac{1}{2}gt^2\Rightarrow t=\sqrt{\dfrac{2h}{g}}=\sqrt{\dfrac{2.10}{10}}=\sqrt{2}\left(s\right)\)

Chọn B

8⁵ : 2¹⁴ = (2³)⁵ : 2¹⁴ = 2^3.5 : 2¹⁴ = 2¹⁵ : 2¹⁴ = 2

x , y có phải là số tự nhiên ko

X,y nguyên nhé bạn

1) 2x+5xy-5y=14 suy ra 2x+5y(x-1)=14 suy ra 2x - 2 + 5y(x-1)=14-2 suy ra 2(x-1)+5y(x-1)=12 suy ra (2+5y)(x-1)=12

vì x , y là số nguyên nên mà 2+5y chia 5 dư 2 nên có 3 trường hợp

vậy (x;y)=(7;0),(2;2),(-3;-1)

nhớ k cho mình đấy

\(88:11=\dfrac{88}{11}=8;144:12=\dfrac{144}{12}=12;1078:14=\dfrac{1078}{14}=77;5545:123=\dfrac{5545}{123}=45\) dư 10

\(\dfrac{88}{11}\)=\(8\)

\(\dfrac{144}{12}\)=\(12\)

\(\dfrac{1078}{14}\)=\(77\)

\(\dfrac{5545}{123}\)=\(45.1\) \(hay\) \(45\)\((dư \) \(10)\)

88:11=88/11=8
144:12=144/12=12
1078:14=1078/14=77
5545:123=5545/123=45(dư10)