Bài1: phân tích đa thức thành nhân tử
1) 21x^2y - 12xy^2
2) x^3 + x^2 - 2x
3) 3x. (x - 1) + 7x^2. (x - 1)
4) 3x. (x-a) + 4a. (a-x)
5) 1/2x. (x-2) + 4a. (a-x)
6) 21. (x-y)^2 - 7.(y-x)
7) x^2yz + xy^2z^2 + x^2yz^2
8) 9x^2y^2 + 15x^2y - 21xy^2
9) x^2y^2 - 1
10) x^4y^4 - z^4
11) (x+1)^2 - 24
12) (x+1)^2 - (y+6)^2
13) x^6 + 1
14) -4y^2 + 4y - 1
15) (2a + 3)^2 - (2a + 1)^2
Bài2: tìm x, biết:
a) x^4 - 16x =0
b) x. (x-3) - x +3 =0
c) 4x^2 - 1/4 =0
d) x^3 - 3x^2 + 3x - 1=0
e) 8x^3 - 36x^2 + 54x - 27=0
f) x^2 + 4x = -4
g) x^2 = 6x - 9
Bài 2;
\(a)x^4-16x=0\Rightarrow x^4=16x\Leftrightarrow x^3=16\Leftrightarrow x=\sqrt[3]{16}\)
\(c)4x^2-\frac{1}{4}=0\Leftrightarrow4x^2=\frac{1}{4}\Leftrightarrow x^2=\frac{1}{16}\Leftrightarrow\hept{\begin{cases}x=\frac{1}{4}\\x=-\frac{1}{4}\end{cases}}\)