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\(x^3+3x^2-4\)
\(=\left(x^3+4x^2\right)-\left(x^2+4\right)\)
\(=\left(x^2+4\right)\left(x-1\right)\)
Mình nhìn nhầm đề
\(x^3+3x^2-4\)
\(=\left(x^3+2x^2\right)+\left(x^2-4\right)\)
\(=x^2\left(x+2\right)+\left(x-2\right)\left(x+2\right)\)
\(=\left(x+2\right)\left(x^2+x-2\right)\)
\(=\left(x+2\right)\left[\left(x^2+x\right)-\left(2x+2\right)\right]\)
\(=\left(x+2\right)\left(x+2\right)\left(x-1\right)\)
\(=\left(x+2\right)^2\left(x-1\right)\)
a)x3+x2+4
=x3-x2+2x+2x2-2x+4
=x(x2-x+2)+2(x2-x+2)
=(x+2)(x2-x+2)
b)x3-2x-4
=x3+2x2+2x-2x2-4x-4
=x(x2+2x+2)-2(x2+2x+2)
=(x-2)(x2+2x+2)
a)3x2+7x-6
=3x2-2x+9x-6
=x(3x-2)+3(3x-2)
=(x+3)(3x-2)
b)8x2-2x-3
=8x2-6x+4x-3
=2x(4x-3)+(4x-3)
=(2x+1)(4x-3)
c)6x2-15x+6
=3(2x2-5x+2)
=3(2x2-x-4x+2)
=3[x(2x-1)-2(2x-1)]
=3(x-2)(2x-1)
d)10x2+7x-6
=10x2+12x-5x-6
=2x(5x+6)-(5x+6)
=(2x-1)(5x+6)
a)2x2+3x-5
=2x2+5x-2x-5
=x(2x+5)-(2x+5)
=(x-1)(2x+5)
b)x8+x4+1
=(x4)2+2x4+1-x4
=(x4+1)2-x4
=(x4+1-x2)(x4+x2+1)
=(x4-x2+1)(x2-x+1)(x2+x+1)
Bài giải:
a) x2 – 3x + 2 = a) x2 – x - 2x + 2 = x(x - 1) - 2(x - 1) = (x - 1)(x - 2)
Hoặc x2 – 3x + 2 = x2 – 3x - 4 + 6
= x2 - 4 - 3x + 6
= (x - 2)(x + 2) - 3(x -2)
= (x - 2)(x + 2 - 3) = (x - 2)(x - 1)
b) x2 + x – 6 = x2 + 3x - 2x – 6
= x(x + 3) - 2(x + 3)
= (x + 3)(x - 2).
c) x2 + 5x + 6 = x2 + 2x + 3x + 6
= x(x + 2) + 3(x + 2)
= (x + 2)(x + 3)
a) \(x^3+4x^2-21x\)
\(=x\left(x^2+4x-21\right)\)
\(=x\left(x^2-3x+7x-21\right)\)
\(=x\left[x\left(x-3\right)+7\left(x-3\right)\right]\)
\(=x\left(x-3\right)\left(x+7\right)\)
b) \(5x^3+6x^2+x\)
\(=x\left(5x^2+6x+1\right)\)
\(=x\left(5x^2+5x+x+1\right)\)
\(=x\left[5x\left(x+1\right)+\left(x+1\right)\right]\)
\(=x\left(x+1\right)\left(5x+1\right)\)
c) \(x^3-7x+6\)
\(=x^3+2x^2-3x-2x^2-4x+6\)
\(=x\left(x^2+2x-3\right)-2\left(x^2+2x-3\right)\)
\(=\left(x-2\right)\left(x^2+2x-3\right)\)
\(=\left(x-2\right)\left(x-1\right)\left(x+3\right)\)
d) \(3x^3+2x-5\)
\(=3x^3+3x^2+5x-3x^2-3x-5\)
\(=x\left(3x^2+3x+5\right)-\left(3x^2+3x+5\right)\)
\(=\left(x-1\right)\left(3x^2+3x+5\right)\)
a)\(2x^2+x-6=2x^2+4x-3x-6=\left(x+2\right)\left(2x-3\right)\)
b)\(6x^4+7x^2+2=6x^4+4x^2+3x^2+2=\left(3x^2+2\right)\left(2x^2+1\right)\)
c)\(2x^2-3x-2700=2x^2+72x-75x+2700=\left(2x-75\right)\left(x+36\right)\)