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\(3x^2-6x+9x^2=12x^2-6x=6x\left(2x-1\right)\)
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a) \(x^3+9x^2+27x+27=\left(x+3\right)^3\)
b) \(3\sqrt{3x^3}+18x^2+12\sqrt{3x}+8=\left(\sqrt{3x}+2\right)^3\)
c) \(\dfrac{1}{4}-x^2=\left(\dfrac{1}{2}-x\right)\left(\dfrac{1}{2}+x\right)\)
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MIK giải đc nhưng ngại lắm , mỏi tay ,đáp số nè:
\(\left(x^2-x-1\right)\left(2x^2+5x-2\right)\)
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a: \(x^2-y^2+3x+3y\)
\(=\left(x^2-y^2\right)+\left(3x+3y\right)\)
\(=\left(x-y\right)\left(x+y\right)+3\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y+3\right)\)
b: Sửa đề: \(x^2-4y^2+4x+4\)
\(=\left(x^2+4x+4\right)-4y^2\)
\(=\left(x+2\right)^2-\left(2y\right)^2\)
\(=\left(x+2+2y\right)\left(x+2-2y\right)\)
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\(a,x^2-5x+6\\=x^2-3x-2x+6\\=x(x-3)-2(x-3)\\=(x-3)(x-2)\\---\\b,3x^2+9x-30\\=3x^2-6x+15x-30\\=3x(x-2)+15(x-2)\\=(x-2)(3x+15)\\=3(x-2)(x+5)\\---\)
\(c,x^2-3x+2\\=x^2-x-2x+2\\=x(x-1)-2(x-1)\\=(x-1)(x-2)\\---\\d,3x^2-5x-2\\=3x^2-6x+x-2\\=3x(x-2)+(x-2)\\=(x-2)(3x+1)\\Toru\)
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Phân tích đa thức thành nhân tử bằng phương pháp đặt nhân tử chung
(3x + 2)^2 + (3x - 2)^2 - 2(9x^2 - 4)
\(=\left(3x+2\right)^2-2\left(3x+2\right)\left(3x-2\right)+\left(3x-2\right)^2\)
\(=\left(3x+2-\left(3x-2\right)\right)^2\)
\(=\left(3x+2-3x+2\right)^2\)
\(=4^2\)
\(=16\)
\(\left(3x+2\right)^2+\left(3x-2\right)^2-2\left(9x^2-4\right)\)
\(=\left(3x+2\right)^2+\left(3x-2\right)^2-2.\left(3x-2\right)\left(3x+2\right)\)
\(=\left(3x+2-3x+2\right)^2\)
\(=4^2=16\)
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\(\left(x^2-3x+2\right)\left(x^2-9x+20\right)-40=\left(x-1\right)\left(x-2\right)\left(x-4\right)\left(x-5\right)-40\)
\(=\left(x^2-6x+5\right)\left(x^2-6x+8\right)-40\)
Đặt \(t=x^2-6x+5\) thì ta có \(t\left(t+3\right)-40=t^2+3t-40=\left(t+8\right)\left(t-5\right)\)
Suy ra \(\left(x^2-6x+5\right)\left(x^2-6x+8\right)-40=\left(x^2-6x+13\right)\left(x^2-6x\right)=x\left(x-6\right)\left(x^2-6x+13\right)\)
=(3x+2)^2+(3x-2)^2-2(3x-2)(3x+2)
=(3x+2-3x+2)^2
=4^2
=16