kệ mài

Bài 4: 

b: \(=x^2z\left(-1+3-7\right)=-5x^2z=-5\cdot\left(-1\right)^2\cdot\left(-2\right)=10\)

c: \(=xy^2\left(5+0.5-3\right)=2.5xy^2=2.5\cdot2\cdot1^2=5\)

Ở trường mình vẫn chưa học đến đa thức.

M=x²+y²+z²+x²-y²+z²+x²+y²-z²

  =(x²+x²+x²)+(y²-y²+y²)+(z²+z²-z²)

  =3x² + y² + z²

fhfghfgghgjf

Ta có : \(\frac{x}{y+z}+\frac{y}{z+x}+\frac{z}{x+y}=1\) \(\Rightarrow\left(x+y+z\right)\left(\frac{x}{y+z}+\frac{y}{z+x}+\frac{z}{x+y}\right)=x+y+z\)

\(\Rightarrow\frac{x^2}{y+z}+\frac{xy+xz}{y+z}+\frac{y^2}{z+x}+\frac{xy+yz}{z+x}+\frac{z^2}{x+y}+\frac{zx+zy}{x+y}\)\(=x+y+z\)

\(\Rightarrow P+\frac{x\left(y+z\right)}{y+z}+\frac{y\left(x+z\right)}{x+z}+\frac{z\left(x+y\right)}{x+y}=x+y+z\)

\(\Rightarrow P+x+y+z=x+y+z\Rightarrow P=0\)

Vậy P = 0

Đề  sai rồi nếu là vầy thì mình làm dc    x+y+z=1 và x/(y+z)+y/(z+x)+z/(x+y)=1.Tính x^2/(y+z)+y^2/(x+z)+z^2/(x+y)+?

gaaaaaaaaaaaaaaaaaaaaaa

à

\(x\left(y-z\right)-z\left(y-x\right)\)

\(=xy-xz-zy+zx\)

\(=xy-zy=y\left(x-z\right)\)

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

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

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

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

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

a, x(y-z)-z(y-x)=xy-xz-zy+xz

                     =xy-zy=y(x-z)

b,(x+y)(x-y)=x²-y²

c,(x+y)²-(x-y)²=(x+y+x-y)(x+y-x+y)

                     =2x.2y

                    =4xy

a) x.(y-z)-z.(y-x) = (xy-xz)-(zy-zx)=xy-xz-zy+zx=xy-zy=y.(x-z)

b)(x+y).(x-y)=(x^2-xy)+(yx-y^2)=x^2-xy+yx-y^2=x^2-y^2

c)(x+y)^2 - (x-y)^2 = (x+y).(x+y) - (x-y).(x-y)=[(x^2+xy)+(yx+y^2)] - [(x^2-xy)-(yx-y^2]=(x^2+xy+yx+y^2)-(x^2-xy-yx+y^2)

=x^2+xy+yx+y^2-x^2+xy+yx-y^2=xy+yx+xy+yx = 4xy

k mình nha!

ngu dễ mà không biết làm mày là đồ con lợn

chịu mới có lớp 7