Viết các biểu thức sau dưới dạng tích:
a) x^3 + 27
b) x^3 - 1/8
c) 8x^3+ y^3
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a) \(8y^3+1\)
\(=\left(2y\right)^3+1^3\)
\(=\left(2y+1\right)\left(4y^2-2y+1\right)\)
b) \(y^3-8\)
\(=y^3-2^3\)
\(=\left(y-2\right)\left(y^2+2y+4\right)\)
`8y^3 + 1 = (2y+1)(4y^2 - 2y + 1)`
`y^3 -8 =(y-2)(y^2+2y+4)`
a: \(\left(x+y+z\right)^2-\left(y+z\right)^2\)
\(=\left(x+y+z-y-z\right)\left(x+y+z+y+z\right)\)
\(=x\left(x+2y+3z\right)\)
b: \(\left(x+3\right)^2+4\left(x+3\right)+4\)
\(=\left(x+3+2\right)^2\)
\(=\left(x+5\right)\left(x+5\right)\)
c: \(25+10\left(x+1\right)+\left(x+1\right)^2\)
\(=\left(x+1+5\right)^2\)
\(=\left(x+6\right)\left(x+6\right)\)
A) \(x^3+27\)
\(=x^3+3^3\)
\(=\left(x+3\right)\left(x^2-3x+9\right)\)
B) \(x^3-\dfrac{1}{8}\)
\(=x^3-\left(\dfrac{1}{2}\right)^3\)
\(=\left(x-\dfrac{1}{2}\right)\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)
C) \(8x^3+y^3\)
\(=\left(2x\right)^3+y^3\)
\(=\left(2x+y\right)\left(4x^2-2xy+y^2\right)\)
D) \(8x^3-27y^3\)
\(=\left(2x\right)^3-\left(3y\right)^3\)
\(=\left(2x-3y\right)\left(4x^2+6xy+9y^2\right)\)
a)\(\left(x+3\right)\left(x^2-3x+9\right)\)
b)\(\left(x-\dfrac{1}{2}\right)\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)
c)\(\left(2x+y\right)\left(4x^2-2xy+y^2\right)\)
d)\(\left(2x-3y\right)\left(4x^2+6xy+9y^2\right)\)
a, \(25+10x+x^2=5^2+2.5x+x^2=\left(5+x\right)^2\)
b, \(8x^3-\dfrac{1}{8}=\left(2x\right)^3-\left(\dfrac{1}{2}\right)^3=\left(2x-\dfrac{1}{2}\right)\left[\left(2x\right)^2+2x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\right]=\left(2x-\dfrac{1}{2}\right)\left(4x^2+x+\dfrac{1}{4}\right)\)
c, \(x^2-10x+25=x^2-2.5x+5^2=\left(x-5\right)^2\)
1. \(25+10x+x^2\\ \Leftrightarrow5^2+2\cdot5\cdot x+x^2\\ \Leftrightarrow\left(5+x\right)^2\\ \Leftrightarrow\left(5+x\right)\left(5+x\right)\)
2. \(8x^3-\dfrac{1}{8}\\ \Leftrightarrow\left(2x\right)^3-\left(\dfrac{1}{2}\right)^3\\ \Leftrightarrow\left(2x-\dfrac{1}{2}\right)\left[\left(2x\right)^2+2x\cdot\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\right]\\ \Leftrightarrow\left(2x-\dfrac{1}{2}\right)\left[4x^2+x+\dfrac{1}{4}\right]\)
3. \(x^2-10x+25\\ \Leftrightarrow x^2-2\cdot5\cdot x+5^2\\ \Leftrightarrow\left(x-5\right)^2\\ \Leftrightarrow\left(x-5\right)\left(x-5\right)\)
2:
-8x^6-12x^4y-6x^2y^2-y^3
=-(8x^6+12x^4y+6x^2y^2+y^3)
=-(2x^2+y)^3
3:
=(1/3)^2-(2x-y)^2
=(1/3-2x+y)(1/3+2x-y)
\(a,27-x^3\)
\(=3^3-x^3\)
\(=\left(3-x\right)\left(9+3x+x^2\right)\)
Các câu còn lại lm tương tự nhé.
hok tốt!
a) \(27-x^3=\left(3-x\right)\left(9+3x+x^2\right)\)
b) \(8x^3+0,001=\left(2x+0,1\right)\left(4x^2-0,2x+0,01\right)\)
c) \(\frac{x^3}{125}-\frac{y^3}{27}=\left(\frac{x}{5}-\frac{y}{3}\right)\left(\frac{x^2}{25}+\frac{xy}{15}+\frac{y^2}{9}\right)\)
p/s: chúc bạn học tốt
\(a,=\left(x+4\right)^2\\ b,=\left(x-6\right)^2\\ c,=-\left(4x^2-4x+1\right)=-\left(2x-1\right)^2\\ d,=\left(x-1\right)^3\)
a: \(x^3+27=\left(x+3\right)\left(x^2-3x+9\right)\)
b: \(x^3-\dfrac{1}{8}=\left(x-\dfrac{1}{2}\right)\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)
c: \(8x^3+y^3=\left(2x+y\right)\left(4x^2-2xy+y^2\right)\)
a) \(\left(x+3\right)\cdot\left(x^2-3x+9\right)\)
b) \(\left(x-\dfrac{1}{2}\right)\cdot\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)
c) \(\left(2x+y\right)\cdot\left(4x^2-2xy+y^2\right)\)