phân tích thành nhân tử: x2-9x+2
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a) (x - 2)(x - 3). b) 3(x - 2)(x + 5).
c) (x - 2)(3x + 1). d) (x-2y)(x - 5y).
e) (x + l)(x + 2)(x - 3). g) (x-1)(x + 3)( x 2 + 3).
h) (x + y - 3)(x - y + 1).
\(c,=x^4+2x^2+1-x^2=\left(x^2+1\right)-x^2=\left(x^2+x+1\right)\left(x^2-x+1\right)\)
giải bài toán: cho tam giác MNP, NTlà phân giác của góc N biết MN=4cm, NT=10cm, MP=8cm:TínhTM, TP?
a: \(3ab-6a^2b\)
\(=3ab\cdot1-3ab\cdot2a\)
=3ab(1-2a)
b: \(x^3-6x\)
\(=x\cdot x^2-x\cdot6\)
\(=x\left(x^2-6\right)\)
c: \(x^2-y^2-9x+9y\)
\(=\left(x^2-y^2\right)-\left(9x-9y\right)\)
\(=\left(x-y\right)\left(x+y\right)-9\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-9\right)\)
d: \(5x^2+10xy+5y^2\)
\(=5\left(x^2+2xy+y^2\right)\)
\(=5\left(x+y\right)^2\)
a: Ta có: \(x^2-4y^2-2x-4y\)
\(=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-2y-2\right)\)
c: Ta có: \(x^3+2x^2y-x-2y\)
\(=x^2\left(x+2y\right)-\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-1\right)\left(x+1\right)\)
d: Ta có: \(3x^2-3y^2-2\cdot\left(x-y\right)^2\)
\(=3\left(x-y\right)\left(x+y\right)-2\cdot\left(x-y\right)^2\)
\(=\left(x-y\right)\left(3x+3y-2x+2y\right)\)
\(=\left(x-y\right)\left(x+5y\right)\)
e: Ta có: \(x^3-4x^2-9x+36\)
\(=x^2\left(x-4\right)-9\left(x-4\right)\)
\(=\left(x-4\right)\left(x-3\right)\left(x+3\right)\)
f: Ta có: \(x^2-y^2-2x-2y\)
\(=\left(x-y\right)\left(x+y\right)-2\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-2\right)\)
a) (x - 1)(x - 2). b) 4(x - 2)(x - 7).
c) (x + 2)(2x +1). d) (x - l)(2x - 7).
e) (2x + 3y - 3)(2x - 3y +1). g) (x - 3)( x 3 + x 2 - x +1).
h) (x + y)(x + y-l)(x + y + l).
3) \(x^2\left(x+2y\right)-x-2y\)
\(=x^2\left(x+2y\right)-\left(x+2y\right)\)
\(=\left(x^2-1\right)\left(x+2y\right)\)
\(=\left(x+1\right)\left(x-1\right)\left(x+2y\right)\)
4) \(x^3-4x^2-9x+36\)
\(=\left(x^3-4x^2\right)-\left(9x-36\right)\)
\(=x^2\cdot\left(x-4\right)-9\left(x-4\right)\)
\(=\left(x-4\right)\left(x^2-9\right)\)
\(=\left(x-4\right)\left(x+3\right)\left(x-3\right)\)
\(x^2\left(x+2y\right)-x-2y\\ =x^2\left(x+2y\right)-\left(x+2y\right)\\ =\left(x^2-1\right)\left(x+2y\right)\\ =\left(x-1\right)\left(x+1\right)\left(x+2y\right)\\ ---\\ x^3-4x^2-9x+36\\ =x^2\left(x-4\right)-9\left(x-4\right)\\ =\left(x^2-9\right)\left(x-4\right)\\ =\left(x-3\right)\left(x+3\right)\left(x-4\right)\)
\(=x^2-y^2-9x-9y=\left(x-y\right)\left(x+y\right)-9\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-9\right)\)
\(\left(x^2-2.\frac{9x}{2}+\left(\frac{9}{2}\right)^2\right)+2-\frac{81}{4}\)
\(\left(x-\frac{9}{2}\right)^2-\frac{73}{4}=\left(x-\frac{9}{2}-\sqrt{\frac{73}{4}}\right)\left(x-\frac{9}{2}+\sqrt{\frac{73}{4}}\right)\)
P/S : h cho chua Pain