Tìm x biết
b) x 52 ¯ + 13 x ¯ = 384
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Áp dụng tc dtsbn:
\(3x=7y\Rightarrow\dfrac{x}{7}=\dfrac{y}{3}=\dfrac{x-y}{7-3}=\dfrac{-16}{4}=-4\\ \Rightarrow\left\{{}\begin{matrix}x=-28\\y=-12\end{matrix}\right.\)
b) \(\Leftrightarrow3x^3+12x-2x^2-8=0\\ \Leftrightarrow\left(3x^3-2x^2\right)+\left(12x-8\right)=0\\ \Leftrightarrow x^2\left(3x-2\right)+4\left(3x-2\right)=0\\ \Leftrightarrow\left(x^2+4\right)\left(3x-2\right)=0\)
Vì \(x^2+4>0\Rightarrow3x-2=0\Rightarrow x=\dfrac{2}{3}\)
c) \(x^2+5x=0\\ \Leftrightarrow x\left(x+5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)
d) \(\Leftrightarrow x^3-27+x\left(4-x^2\right)=36\\ \Leftrightarrow x^3+4x-x^3=63\\ \Leftrightarrow4x=63\\ \Leftrightarrow x=\dfrac{63}{4}\)
b) 3x(x\(^3\) +12x-2x\(^2\)-8=0
3x(x\(^2\)+4)-2(x\(^2\)+4)=0
(x\(^2\)+4)(3x-2)=0
\(\Leftrightarrow\left[{}\begin{matrix}X^2+4=0\\3X-2=0\end{matrix}\right.\) <=> \(\left[{}\begin{matrix}x\in Z\\X=\dfrac{2}{3}\end{matrix}\right.\)
a) x\(^2\)+5x=0
x(x+5)=0
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+5=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)
c)(x-3)(x\(^2\)+3x+9)+x(x+2)(2-x)=36
x\(^3\)-27+x(x+2)(2-x)=36
4x-27=36
4x=36+27
4x=63
x=\(\dfrac{63}{4}\)
(7 - x) + (10 -x) + (13 - x) + ... + (52 - x) + (55 - x) = 493
<=>7+10+13+...+55-17x=493
<=>(55+7).17:2 - 17x=493
<=>527-17x=493
<=>x=2
14 x X + 25 x X - 13 x X = 52
X x ( 14 + 25 - 13 ) = 52
X x 26 = 52
X = 52 : 26
X = 2
X x (14 + 25 - 13) = 52
X x 26 = 52
X = 52 : 26
X = 2
Chúc em học tốt <3
B-(\(3x^6-4xy^5+\dfrac{1}{3}xy^2\))=
B= \(\left(7x^6-\dfrac{1}{2}xy^5-xy^2-\dfrac{1}{3}\right)+\left(3x^6-4xy^5+\dfrac{1}{3}xy^2-\dfrac{3}{2}\right)\)
B= \(7x^6-\dfrac{1}{2}xy^5-xy^2-\dfrac{1}{3}+3x^6-4xy^5+\dfrac{1}{3}xy^2-\dfrac{3}{2}\)
B= \(7x^6+3x^6-\dfrac{1}{2}xy^5-4xy^5-xy^2+\dfrac{1}{3}xy^2-\dfrac{1}{3}+\dfrac{2}{3}\)
B= \(10x^6-\dfrac{9}{2}xy^5-\dfrac{2}{3}xy^2+\dfrac{1}{3}\)
\(\frac{x}{13}:\frac{15}{16}=\frac{46}{52}\)
\(\Rightarrow\frac{x}{13}=\frac{46}{52}\cdot\frac{15}{16}=\frac{23}{26}\cdot\frac{15}{16}\)
\(\Rightarrow\frac{x}{13}=\frac{345}{416}\)
\(\Rightarrow x=\frac{345}{416}\cdot13=\frac{345}{32}\)
Vậy \(x=\frac{345}{32}\)
K MK ĐI. ~ HỌC TỐT NHA ~
\(\frac{x}{13}:\frac{15}{16}=\frac{46}{52}\)
\(\Rightarrow\frac{x}{13}:\frac{15}{16}=\frac{23}{26}\)
\(\Rightarrow\frac{x}{13}=\frac{23}{26}\times\frac{15}{16}\)
\(\Rightarrow\frac{x}{13}=\frac{345}{416}\)
\(\Leftrightarrow416\times x=13\times345\)
\(\Rightarrow416\times x=4485\)
\(\Rightarrow x=4485:416\)
\(\Rightarrow x=\frac{345}{32}\)
x/3 + 15/26 = 46/52
x/13 + 15/26 = 23/26
x/13 = 23/26 - 15/26
x/13 = 4/13
Có x/13 = 4/13
Suy ra : x = 4
Vậy x = 4