Phân tích thành nhân tử
x+4
x√x-1
2+√3+√6+√8
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\(\left(x+2\right)\left(x+3\right)\left(x+8\right)\left(x+12\right)-4x^2\)
\(=\left(x+2\right)\left(x+12\right)\left(x+3\right)\left(x+8\right)-4x^2\)
\(=\left(x^2+14x+24\right)\left(x^2+11x+24\right)-\left(2x\right)^2\)
Đặt \(x^2+11x+24=a\)
\(=a\left(a+3x\right)-4x^2=a^2+3ax-4x^2=a^2-ax+4ax-4x^2=\left(a-x\right)\left(a+4x\right)\)
\(x^2+2x-8\)
\(=x^2+4x-2x-8\)
\(=x^2\left(x+4\right)-2\left(x+4\right)\)
\(=\left(x^2-2\right)\left(x+4\right)\)
\(x^2+5x+6\)
\(=x^2+2x+3x+6\)
\(=x\left(x+2\right)+3\left(x+2\right)\)
\(=\left(x+3\right)\left(x+2\right)\)
\(4x^2-12x+8\)
\(=4x^2-4x-8x+8\)
\(=4x\left(x-1\right)-8\left(x-1\right)\)
\(=\left(4x-8\right)\left(x-1\right)\)
\(x^2-xy-\dfrac{3}{4}y^2\)
\(=x^2-\dfrac{3}{2}xy+\dfrac{1}{2}xy-\dfrac{3}{4}y^2\)
\(=x\left(x-\dfrac{3}{2}y\right)+\dfrac{1}{2}y\left(x-\dfrac{3}{2}y\right)\)
\(=\left(x+\dfrac{1}{2}y\right)\left(x-\dfrac{3}{2}y\right)\)
a)\(7x\left(y-4\right)^2-\left(4-y\right)^3=7x\left(4-y\right)^2-\left(4-y\right)^3=\left(4-y\right)^2\left(7x-4+y\right)\)
b)\(\left(4x-8\right)\left(x^2+6\right)-\left(4x-8\right)\left(x+7\right)+9\left(8-4x\right)\)
\(=\left(4x-8\right)\left(x^2+6\right)-\left(4x-8\right)\left(x+7\right)-9\left(4x-8\right)\)
\(=\left(4x-8\right)\left(x^2-x-10\right)=4\left(x-2\right)\left(x^2-x-10\right)\)
a.\(7x.\left(y-4\right)^2-\left(4-y\right)^3\)=\(7x.\left(4-y\right)^2-\left(4-y\right)^3=\left(4-y\right)^2.\left(7x+y-4\right)\)
b.\(\left(4x-8\right).\left(x^2+6\right)-\left(4x-8\right)\left(x+7\right)+9.\left(8-4x\right)\)
=\(\left(4x-8\right)\left(x^2+6-x-7-9\right)=\left(4x-8\right)\left(x^2-x-10\right)\)
x^2(x-3)+12-4x = x^2(x-3)+4(3-x) = x^2(x-3)-4(x-3) = (x-3)(x^2-4) = (x-3)(x-2)(x+2)
n^3-n=n(n^2-1) = n(n+1)(n-1)
Ta thấy tích trên là tích 3 số tự nhiên liên tiếp luôn chia hết cho 6
Vậy n^3-n luôn chia hết cho 6
ta có
\(5x=-3y=4z\)
\(\Rightarrow\frac{x}{12}=-\frac{y}{20}=\frac{z}{15}\)
\(\Rightarrow\frac{x}{12}=-\frac{y}{20}=\frac{3z}{45}=\frac{x-y+3z}{12+20+45}=\frac{7}{77}=\frac{1}{11}\)
\(\Rightarrow\hept{\begin{cases}x=\frac{1}{11}.12=\frac{12}{11}\\-y=\frac{1}{11}.20=\frac{20}{11}\\3z=\frac{1}{11}.45=\frac{45}{11}\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x=\frac{12}{11}\\y=-\frac{20}{11}\\z=\frac{45}{11}:3=\frac{15}{11}\end{cases}}\)
Vậy \(\hept{\begin{cases}x=\frac{12}{11}\\y=\frac{-20}{11}\\z=\frac{15}{11}\end{cases}}\)
\(x^2\left(x-3\right)+4\left(3-x\right)\)\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x^2-4\right)\left(x-3\right)\)\(=\left(x-2\right)\left(x+2\right)\left(x-3\right)\)
\(x^2\left(x-3+12-4x\right)\)
\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-4\right)\)
\(=\left(x-3\right)\left(x-2\right)\left(x+2\right)\)
( 4x - 8 ) . ( x2 + 6 ) - ( 4x - 8 ) . ( x + 7 ) + 9 . ( 8 - 4x )
= (4x - 8 ) . ( x2 + 6 ) - ( 4x - 8 ) . ( x + 7 ) - 9 . (4x - 8)
= (4x-8) ( x2+6 - x - 7 - 9)
= 4(x-2)(x^2 -x - 10)
a) \(x^{12}-y^4=\left(x^6\right)^2-\left(y^2\right)^2=\left(x^6-y^2\right)\left(x^6+y^2\right)=\left(x^3-y\right)\left(x^3+y\right)\left(x^6+y^2\right)\)
b) \(x^9+1=\left(x^3\right)^3+1=\left(x^3+1\right)\left(x^6-x^3+1\right)=\left(x+1\right)\left(x^6-x^3+1\right)^2\)
c) \(x^6-y^6=\left(x^2\right)^3-\left(y^2\right)^3=\left(x^2-y^2\right)\left(x^4-x^2y^2+y^4\right)=\left(x-y\right)\left(x+y\right)\left(x^4-x^2y^2+y^4\right)\)
d) \(x^6+1=\left(x^2\right)^3+1=\left(x^2+1\right)\left(x^4-x^2+1\right)\)
e) \(9x^6-12x^7+4x^8=x^6\left(9-12x+4x^2\right)=x^6\left(3-2x\right)^2\)