1, TÍNH 

a, 8.16 : ( 1.24+3.56) - 0.236*0.25

=8.16:4.8-0.059

=1.7-0.059

=1.641

b,(0.872:2.18+4.05*3)-3.03*2.1

=(0.4+12.15)-6.363

= 12.55-6.363

=6.187

2, TÌM x

b, x * 3,18 = 56,019 - 16,11

=> x*3.18= 39,909

=> x       = 39,909:3,18

=> x       =     12,55

c, 4,7 * x =48,88:2

=>4,7 * x = 24,44

=>x         =24,44:4,7

=>x         = 5,2     

1.tính:

a) 8,16 :( 1,24 + 3,56 ) - 0 ,236 * 0,25

=  8,16 :      4,80         - 0 ,236 * 0,25

=      1,7                     - 0 ,059

=       1,641

b) (0,872: 2,18 + 4,05 * 3) - 3,02 * 2,1

=   13,35                         - 3,02 * 2,1

=   13,35                         - 6,342

=    7,008

các bạn làm nhanh hộ mình nhé rồi mình k cho nha cảm ơn nhiều nhé!

`(x^4-1)^2+(x^2+1)^2`

`=x^8-2x^4+1+x^4+2x^2+1`

`=x^8-x^4+2x^2+2`

\(\left(x^4-1\right)^2+\left(x^2+1\right)^2=\left(x^2-1\right)^2.\left(x^2+1\right)^2+\left(x^2+1\right)^2\)

\(=\left(x^2+1\right)^2\left[\left(x^2-1\right)^2+1\right]=\left(x^2+1\right)^2\left(x^4-2x^2+2\right)\)

`(x^4-1)^2+(x^2+1)^2`

`=[(x^2)^2-1^2]^2+(x^2+1)^2`

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

`=(x^2+1)^2 [(x^2-1)^2+1]`

Bài 1 : 

\(\frac{x}{2}=\frac{y}{3};\frac{y}{4}=\frac{z}{5}\Rightarrow\frac{x}{8}=\frac{y}{12}=\frac{z}{15}\)

Theo tính chất dãy tỉ số bằng nhau 

\(\frac{x}{8}=\frac{y}{12}=\frac{z}{15}=\frac{x+y-z}{8+12-15}=\frac{10}{5}=2\Rightarrow x=16;y=24;z=30\)

bài 2 : 

Đặt \(x=2k;y=5k\Rightarrow xy=10k^2=10\Leftrightarrow k^2=1\Leftrightarrow k=\pm1\)

Với k = 1 thì x = 2 ; y = 5

Với k = - 1 thì x = -2 ; y = -5

x+4⋮x-2

x-2+6⋮x-2

x-2⋮x-2 ⇒6⋮x-2

x-2∈Ư(6)

Ư(6)={1;-1;2;-2;3;-3;6;-6}

x∈{3;1;4;0;5;-1;8;-4}

\(x+4⋮x-2\Leftrightarrow\left(x-2\right)+6⋮x-2\)

Có: \(x-2⋮x-2\Rightarrow6⋮x-2\)

\(\Rightarrow x-2\inƯ\left(6\right)=\left\{\pm1;\pm2;\pm3\pm6\right\}\)

\(\Rightarrow x=\left\{1;3;0;4;-1;5;-4;8\right\}\)

\(x\times3,12-x=3,18\)

\(3,12x-x=3,18\)

\(2,12x=3,18\)

\(x=3,18\div2,12\)

\(x=1,5\)

\(x\times3,12-x=3,18\)

\(x\times\left(3,12-1\right)=3,18\)

\(x\times2,12=3,18\)

            \(x=3,18:2,12\)

            \(x=1,5\)

a) A= 3.(x²-2xy+y²)- 2. (x²+2xy+y²) - x²-y²

A= 3.x²-2xy+y²-2. x²+2xy+y²-x²-y²

\(=1\cdot\left(-1\right)+\left(-1\right)^2\cdot2^2+1^3\cdot2^3=8-1+4=11\)

a) \(3\left(x-y\right)^2+9y\left(y-x\right)^2\)

\(=3\left(x-y\right)^2+9y\left(x-y\right)^2\)

\(=\left(x-y\right)^2\left(3-9y\right)\)

\(=3\left(x-y\right)^2\left(3y+1\right)\)

b) \(3\left(x-y\right)^2+9y\left(y-x\right)\)

\(=3\left(y-x\right)^2+9y\left(y-x\right)\)

\(=\left(y-x\right)\left[3\left(y-x\right)+9y\right]\)

\(=3\left(y-x\right)\left(y-x+3y\right)\)

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

a: =3(x-y)^2+9y(x-y)^2

=(x-y)^2(3+9y)

=(x-y)^2*3*(y+3)

b: =3(x-y)^2-9y(x-y)

=3(x-y)(x-y-9y)

=3(x-y)(x-10y)