Question

[mai Trương]

hẹp mi với ạ 

Answer 1

[HaNa]

Bài 5:

a)

\(x^4+x^3+x+1\\ =x^3\left(x+1\right)+\left(x+1\right)\\ =\left(x^3+1\right)\left(x+1\right)\)

b)

\(x^4-x^3-x+1\\ =x^3\left(x-1\right)-\left(x-1\right)\\ =\left(x^3-1\right)\left(x-1\right)\\ =\left(x-1\right)\left(x^2+x+1\right)\left(x-1\right)\)

c)

\(3x^2-12y^2\\ =\left(\sqrt{3}x\right)^2-\left(\sqrt{12}y\right)^2\\ =\left(\sqrt{3}x-\sqrt{12}y\right)\left(\sqrt{3}x+\sqrt{12}y\right)\\ =\sqrt{3}\left(x-\sqrt{4}y\right).\sqrt{3}\left(x+\sqrt{4}y\right)\\ =3\left(x-\sqrt{4}y\right)\left(x+\sqrt{4}y\right)\)

Answer 2

[Nguyễn Lê Phước Thịnh]

7:

a: (2x-1)^2-25=0

=>(2x-1)^2=25

=>2x-1=-5 hoặc 2x-1=5

=>2x=6 hoặc 2x=-4

=>x=-2 hoặc x=3

b: 8x^3-50x=0

=>4x^3-25x=0

=>x(4x^2-25)=0

=>x(2x-5)(2x+5)=0

=>x=0 hoặc 2x-5=0 hoặc 2x+5=0

=>x=0;x=5/2;x=-5/2

c: 3x(x-1)+(x-1)=0

=>(x-1)(3x+1)=0

=>x=1 hoặc x=-1/3

d: =>2(x+3)-x(x+3)=0

=>(x+3)(2-x)=0

=>x=-3 hoặc x=2

e: Thiếu vế phải rồi bạn

f: x^3+27+(x+3)(x-9)=0

=>(x+3)(x^2-3x+9)+(x+3)(x-9)=0

=>(x+3)(x^2-3x+9+x-9)=0

=>(x+3)(x^2-2x)=0

=>x(x-2)(x+3)=0

=>\(x\in\left\{0;2;-3\right\}\)