a)
\(=\left(x+2y\right)\left(x^2-xy+y^2\right)-3xy\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x^2-xy+y^2-3xy\right)\)
\(=\left(x+2y\right)\left(x^2-2xy+y^2\right)\)
\(=\left(x+2\right)\left(x-2\right)^2\)
b)
\(3x\left(2x-1\right)\left(2x+1\right)=0\)
3x=0 =>x=0
hoặc 2x-1=0 => 2x=1=>x=1/2
hoặc 2x+1=0=>2x=-1=>x=-1/2
(x+5)2-(x+5)(x-2)=0
x3+7x2+6x=0
(x+1)2-(2x+3)2=0
Bài 4: Tìm x, biết.
a) 4x(x - 7) - 4x2 = 56
b) 12x(3x - 2) - (4 - 6x) = 0
c) 4(x - 5) - (5 - x)2 = 0
d) x(x +1) - x(x - 3) = 0
e) - 6x + 8 = 0 f) 2 + 2x + = 0
Gỉai các phương trình sau;
a, 3x2 - 8x2 - 2x + 3 = 0
b, (x2 - 1)2 = 4x +1
c, 2x3 + 7x2 + 7x + 2 = 0
d, 2x3 - 9x + 2 = 0
e, 8x3 - 4x2 + 10x - 5 = 0
g. x3 + x2 - x√22 - 2√22= 0
h. (x +1 )2 = 9(x - 1)2
Bài 5. Tìm x, biết:
a) x (2x - 7) + 4x -14 = 0
b) x3 - 9x = 0
c) 4x2 -1 - 2(2x -1)2 = 0
d) (x3 - x2 ) - 4x2 + 8x - 4 = 0
. Tìm x, biết:
a) 4x2 – 9 = 0
b) (x + 5)2 – (x – 1)2= 0
c) x2 – 6x – 7 = 0
d) (x + 1)2 – (2x - 1)2 = 0
Tính
1. ( - 4xy ) . ( 2xy2 - 3x2y)
2. ( -5x ) ( 3x3 + 7x2 - x )
3. ( 3x - 2 ) ( 4x + 5 ) - 6x ( 2x -1 )
4. 2x2 ( x2 - 7x + 9 )
5. ( 3x - 5 ) ( x2 - 5x + 7 )
Giải các phương trình tích sau:
1.a)(3x – 2)(4x + 5) = 0 b) (2,3x – 6,9)(0,1x + 2) = 0
c)(4x + 2)(x2 + 1) = 0 d) (2x + 7)(x – 5)(5x + 1) = 0
2. a)(3x + 2)(x2 – 1) = (9x2 – 4)(x + 1)
b)x(x + 3)(x – 3) – (x + 2)(x2 – 2x + 4) = 0
c)2x(x – 3) + 5(x – 3) = 0 d)(3x – 1)(x2 + 2) = (3x – 1)(7x – 10)
3.a)(2x – 5)2 – (x + 2)2 = 0 b)(3x2 + 10x – 8)2 = (5x2 – 2x + 10)2
c)(x2 – 2x + 1) – 4 = 0 d)4x2 + 4x + 1 = x2
4. a) 3x2 + 2x – 1 = 0 b) x2 – 5x + 6 = 0
c) x2 – 3x + 2 = 0 d) 2x2 – 6x + 1 = 0
e) 4x2 – 12x + 5 = 0 f) 2x2 + 5x + 3 = 0
Tìm x biết :
a, (x-2).(x2 +2x +7) +2.( x2-4) -5 .(x-2) =0
b, 4x2 -25 -(2x-5) .(2x+7) =0
c, x3 +27 + (x+3) .(x-9)=0
Bài 2: Tìm x
a) (x-2)2-(2x+3)2=0 d) x2.(x+1)-x.(x+1)+x.(x-1)=0
b) 9.(2x+1)2-4.(x+1)2=0 e) (x-2)2-(x-2).(x+2)=0
c) x3-6x2+9x=0 g) x4-2x2+1=0
h) 4x2+y2-20x-2y+26=0 i) x2-2x+5+y2-4y=0
