Question

Tìm x biết
a,(x+1).(x^2-x+1)-x^3+2x-9=0

b,(x+4)^2-x^2+16=0
Các bạn ơi giúp mình với :( mai mình nộp r

Answer 1

a) PT \(\Leftrightarrow x^3+1-x^3+2x-9=0\)

\(\Leftrightarrow2x=8\) \(\Leftrightarrow x=4\)

Vậy \(x=4\)

b) PT \(\Leftrightarrow\left(x+4\right)^2-\left(x^2-16\right)=0\)

\(\Leftrightarrow8\cdot\left(x+4\right)=0\) \(\Leftrightarrow x=-4\)

Vậy \(x=-4\)

Answer 2

a)

(x+1).(x²-x+1)-x³+2x-9=0

(x+1).(x²-x.1+1²)-x³+2x-9=0

x³+1-x³+2x-9 =0

(x³-x³)+2x+(1-9) =0

2x+8 =0

2.(x+4) =0

x+4 =0

x =-4

b)

(x+4)²-x²+16 =0

(x+4)²-(x²-16) =0

(x+4)²-(x²-4²) =0

(x+4)(x+4)-(x-4)(x+4)=0

(x+4)((x+4)-(x-4)) =0

(x+4)(x+4-x+4) =0

(x+4)8 =0

x+4 =0

x =-4