[x-1]/7=[-3]/[y+3]`

`=>(x-1)(y+3)=-21=-21.1=-1.21=-3.7=-7.3`

`@{(x-1=-21),(y+3=1):}=>{(x=-20),(y=-2):}`

`@{(x-1=-1),(y+3=21):}=>{(x=0),(y=18):}`

`@{(x-1=-3),(y+3=7):}=>{(x=-2),(y=4):}`

`@{(x-1=-7),(y+3=3):}=>{(x=-6),(y=0):}`

tách nhỏ ra

\(\dfrac{6}{8}-\dfrac{2}{7}=\dfrac{42}{56}-\dfrac{16}{56}=\dfrac{26}{56}=\dfrac{13}{28}\)

b) Ta có: \(x^3-x^2y-xy^2+y^3\)

\(=\left(x^3+y^3\right)-\left(x^2y+xy^2\right)\)

\(=\left(x+y\right)\left(x^2-xy+y^2\right)-xy\left(x+y\right)\)

\(=\left(x+y\right)\left(x^2-2xy+y^2\right)\)

\(=\left(x+y\right)\left(x-y\right)^2\)

\(\Leftrightarrow2x^3-3x^2+x+a=\left(x+3\right)\cdot a\left(x\right)\)

Thay \(x=-3\)

\(\Leftrightarrow2\left(-27\right)-3\cdot9-3+a=0\\ \Leftrightarrow-54-27-3+a=0\\ \Leftrightarrow-84+a=0\\ \Leftrightarrow a=84\)

x+1/6=x+8/3

\(\Leftrightarrow\)x-x=8/3-1/6

\(\Leftrightarrow\)0x=15/6 (vô nghiệm)

\(x+\dfrac{1}{6}=x+\dfrac{8}{3}\)

\(x-x=\dfrac{8}{3}-\dfrac{1}{6}=\dfrac{15}{6}\)(vô nghiệm)

`(x+1)/6=(x+8)/3`

`<=> 3(x+1)=6(x+8)`

`<=> 3x+3=6x+48`

`<=> 3x-6x=48-3`

`<=> -3x=45`

`<=> x=-15`

c: Ta có: \(\left(x+1\right)^2\ge0\forall x\)

\(\left(y-\dfrac{1}{3}\right)^2\ge0\forall y\)

Do đó: \(\left(x+1\right)^2+\left(y-\dfrac{1}{3}\right)^2\ge0\forall x,y\)

\(\Leftrightarrow\left(x+1\right)^2+\left(y-\dfrac{1}{3}\right)^2-10\ge-10\forall x,y\)

Dấu '=' xảy ra khi x=-1 và \(y=\dfrac{1}{3}\)

\(2\left(x-3\right)+5⋮x-3\Rightarrow x-3\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

\(=x\in\left\{2;4;8\right\}\)

Thay `x=-1, y=3`

`B=3*(-1)^2*3-6*(-1)^2*3^2+3*(-1)*3^2`

`= 3*3-6*9-3*9`

`= 9-54-27`

`=-72`

Câu này chắc là tính B.

\(B=3x^2y-6x^2y^2+3xy^2\\ B=3xy.\left(x-2xy+y\right)\\ Thay:x=-1;y=3.vàoB:\\ B=3.\left(-1\right).3.\left[-1-2.\left(-1\right).3+3\right]=-3.3.\left(-1+6+3\right)=-9.8=-72\)

Tìm ƯCLN à bạn

1)UCLN là 3

2)UCLN là 4

3) UCLN là 12

4) UCLN là 3

1: UCLN(12;18;9)=3

2: UCLN(8;12;4)=4

b: \(=\dfrac{3a-9-2a-6-6}{\left(a+3\right)\left(a-3\right)}=\dfrac{a-15}{a^2-9}\)