Question

Giải các pt: a) x|x+3| - |x^2+x+1|=1

b) |x|^3 - 3|x| + 2 = 0

Answer 1

b)

|x|=y>=0

y^3-y-2(y-1)=0

<=>(y-1)(y^2+y+1-2)=0

y=1=>x=±1

y^2+y-1=0

(y-1/2)^2=5/4=(√5/2)^2

y=(1+√5)/2

x=±(1+√5)/2

Answer 2

a)x^2+x+2>0

Th1 x< -3 <=>-x^2-3x-x^2-x-1=1

<=>-2x^2-4x-2=0

<=>-(x+1)^2==>x=1(l)

th2x>-3

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

2x=2=>x=1(nhan)

kl

x=1

Answer 3

Câu a:

Answer 4

Câu b