Tìm x biết;a) (2x -1) . (x2-x+1) - 2x3 + 3x2 = 2b) ( x+1) . (x2 + 2x+ 4) - x3 - 3x2 + 16 = 0c) 2(x+1) . (x-3) - 2x2 = 20d) ( x2 - x + 1) . (x+1) - x3 + 3x = 15e) ( x+3) . (x-2) +3x = 4. (x + 3/4)g) (x2 - 5) . ( x + 2 ) + 5x = 2x2 + 17Do k viết đk phân số nên mình sẽ thay bằng dấu...
Đọc tiếp
Tìm x biết;
a) (2x -1) . (x2-x+1) - 2x3 + 3x2 = 2
b) ( x+1) . (x2 + 2x+ 4) - x3 - 3x2 + 16 = 0
c) 2(x+1) . (x-3) - 2x2 = 20
d) ( x2 - x + 1) . (x+1) - x3 + 3x = 15
e) ( x+3) . (x-2) +3x = 4. (x + 3/4)
g) (x2 - 5) . ( x + 2 ) + 5x = 2x2 + 17
Do k viết đk phân số nên mình sẽ thay bằng dấu /
(2x-1)(x2-x+1)-2x3+3x2=2
=>(2x3-2x2+2x-x2+x-1)-2x3+3x2=2
=>2x3-2x2+2x-x2+x-1-2x3+3x2=2
=>2x3-3x2+3x-1-2x3+3x2=2
=>3x-1=2
=>3x=2+1=3
=>x=3:3=1
b)(x+1)(x2+2x+4)-x3-3x2+16=0
=>(x3+2x2+4x+x2+2x+4)-x3-3x2+16=0
=>x3+2x2+4x+x2+2x+4-x3-3x2+16=0
=>x3+3x2+6x+4-x3-3x2+16=0
=>6x+4+16=0
=>6x+20=0
=>6x=0-20=-20
=>x=\(\frac{-20}{6}=\frac{-10}{3}\)