Question

1) Tìm x , biết :

 

a) ( x^2 - x + 1 ) . ( x + 1 ) - x^3 + 3x = 15

 

b) ( x + 3 ) . ( x - 2 ) + 3x = 4( x + 3phần4 )

 

c) ( x^2 - 5 ) . ( x + 2 ) + 5x = 2x^2 + 17

 

_Mọi người giúm em giùm , em cảm ơn rất nhiều ạ !!!

Answer 1

a)\(\left(x^2-x+1\right).\left(x+1\right)-x^3+3x=15\)

\(x^3+x^2-x^2-x+x+1-x^3+3x=15\)

\(1+3x=15\)

\(3x=15-1\)

\(3x=14\)

\(x=\frac{14}{3}\)
 

 

Answer 2

b) \(\left(x+3\right).\left(x-2\right)+3x=4\left(x+\frac{3}{4}\right)\)

\(x^2-2x+3x-6+3x=4x+3\)

\(x^2-2x+3x+3x-4x=6+3\)

\(x^2=9\)

\(x^2=3^2\) hoặc \(x^2=\left(-3\right)^2\)

 vậy x=3 hoặc x=-3

 

Answer 3

a)  \(\left(x^2-x+1\right)\cdot\left(x+1\right)-x^3+3x=15\)

\(x^3-x^2+x+x^2-x+1-x^3+3x=15\)

\(3x+1=15\)

\(x=\frac{14}{3}\)

b) \(\left(x+3\right)\left(x-2\right)+3x=4\left(x+\frac{3}{4}\right)\)

\(x^2+3x-2x-6+3x=4x+3\)

\(x^2=9\)

\(x=+-3\)

c) \(\left(x^2-5\right)\left(x+2\right)+5x=2x^2+17\)

\(x^3-5x+2x^2-10+5x=2x^2+17\)

\(x^3=27\)

\(x=3\)

Answer 4

c)\(\left(x^2-5\right).\left(x+2\right)+5x=2x^2+17\)

\(x^3+2x^2-5x-10+5x=2x^2+17\)

\(x^3+2x^2-5x+5x-2x^2=10+17\)

\(x^3=27\)

\(x^3=3^3\)

vậy x=3

 

Answer 5

câu hỏi này rất hay