x mũ3 - 3x bình y + x+3xy bình -y-y mũ3
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\(x^3-3x^2=0\)
\(\Leftrightarrow x^2\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)
khỉ nghĩ như này..
x3-3x2=0
(=)x2 (x-3)=0
(=)x2=0,hoac x-3=0
(=)x=3
\(\left(2x-1\right)\left(3x+5\right)+\left(-6x^3+5x\right):x\)
\(=6x^2+10x-3x-5-6x^3+5x:x\)
\(=-6x^3+6x^2+12x-5:x\)
\(=-6x^2+6x+12-\dfrac{5}{x}=-6\left(x^2-x-12\right)-\dfrac{5}{x}\)
A = (2\(x\) - 1)(3\(x\) + 5) + (-6\(x\)3 + 5\(x\)): \(x\)
A = 6\(x^2\) + 10\(x\) - 3\(x\) - 5 + \(x\)(- 6\(x^2\) + 5): \(x\)
A = 6\(x^2\) + 7\(x\) - 5 - 6\(x^2\) + 5
A = (6\(x^2\) - 6\(x^2\)) + 7\(x\) - (5 - 5)
A = 7\(x\)
a) \(\left(x-\frac{1}{2}\right)^3=27\)
=> \(\left(x-\frac{1}{2}\right)^3=3^3\)
=> \(x-\frac{1}{2}=3\)
=> \(x=3+\frac{1}{2}\)
=> \(x=\frac{7}{2}\)
Vậy \(x=\frac{7}{2}.\)
b) \(\left(2x-1\right)^3=-27\)
=> \(\left(2x-1\right)^3=\left(-3\right)^3\)
=> \(2x-1=-3\)
=> \(2x=\left(-3\right)+1\)
=> \(2x=-2\)
=> \(x=\left(-2\right):2\)
=> \(x=-1\)
Vậy \(x=-1.\)
Chúc bạn học tốt!
\(1.\left(x^3-1\right)\left(x^2+1\right)=0\)
\(< =>\left\{{}\begin{matrix}x^3-1=0\\x^2+1=0\end{matrix}\right.\)
\(< =>\left\{{}\begin{matrix}x^3=1\\x^2=-1\left(kxđ\right)\end{matrix}\right.\)
<=>x=1
vậy ...
\(2.\left(2x+6\right)\left(3x^2-12\right)=0\)
\(< =>\left\{{}\begin{matrix}2x+6=0\\3x^2-12=0\end{matrix}\right.\)
\(< =>\left\{{}\begin{matrix}2x=-6\\3x^2=12\end{matrix}\right.\)
\(< =>\left\{{}\begin{matrix}x=-3\\x^2=4\end{matrix}\right.\)
\(< =>\left\{{}\begin{matrix}x=-3\\x=2\\x=-2\end{matrix}\right.\)
vậy ...
\(\left(6x-3^3\right).5^3=3.5^4\)
\(\Rightarrow\left(6x-27\right)=3\left(5^4\div5^3\right)\)
\(\Rightarrow\left(6x-27\right)=3.5\)
\(\Rightarrow6x-27=15\)
\(\Rightarrow6x=42\)
\(\Rightarrow x=7\)
`x^3 - 3x^2y + x + 3xy^2 - y - y^3`
`=(x)^3 - 3*(x)^2*y + 3*x*y^2 - (y)^3 + (x - y)`
`= (x - y)^3 + (x - y)`
`= (x - y)[(x - y)^2 + 1]`
`= (x - y)(x - y - 1)(x - y + 1)`
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`@` CT:
`(A - B)^3=A^3-3A^2B+3AB^2- B^3`