Question

Tìm x, biết: 

a. ( x+ 2) ( x^2 - 2x + 4) - x ( x^2+2) = 0

b. ( x+1 ) ( x^2+x+1 ) ( x-1) ( x^2-x+1 ) = 7

c. ( x-1 ) ( x^2+x+1 ) - x ( x+2 ) ( x-2) = 5

mik đang cần gấp

Answer 1

a: \(\Leftrightarrow x^3+8-x^3-2x=0\)

=>-2x+8=0

hay x=4

b: \(\Leftrightarrow\left(x^3+1\right)\left(x^3-1\right)=7\)

\(\Leftrightarrow x^6=8\)

\(\Leftrightarrow x^2=2\)

hay \(x=\pm\sqrt{2}\)

c: \(\Leftrightarrow x^3-1-x^3+4x=5\)

=>4x=6

hay x=3/2

Answer 2

\(a,\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=0.\\ \Leftrightarrow x^3+8-x^3-2x=0.\\ \Leftrightarrow-2x+8=0.\\ \Leftrightarrow x=4.\)

\(c,\left(x-1\right)\left(x^2+x+1\right)-x\left(x+2\right)\left(x-2\right)=5.\\ \Leftrightarrow x^3-1-x\left(x^2-4\right)=5.\\ \Leftrightarrow x^3-1-x^3+4x-5=0.\\ \Leftrightarrow4x-6=0.\\ \Leftrightarrow x=\dfrac{3}{2}.\)