Áp dụng tc dtsbn:

\(3x=7y\Rightarrow\dfrac{x}{7}=\dfrac{y}{3}=\dfrac{x-y}{7-3}=\dfrac{-16}{4}=-4\\ \Rightarrow\left\{{}\begin{matrix}x=-28\\y=-12\end{matrix}\right.\)

x= 6 nhé

tick giúp mik

x=6

x=6

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

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

tớ đang học mấy tính bỏ túi : thanks

-x/13 = -52/x

=> x² = -52.-13 = 676

=> x = 26

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 ~

\(\frac{x}{13}:\frac{15}{16}=\frac{46}{52}\)

\(\Rightarrow\frac{x}{13}:\frac{15}{16}=\frac{23}{26}\)

\(\Rightarrow\frac{x}{13}=\frac{23}{26}\times\frac{15}{16}\)

\(\Rightarrow\frac{x}{13}=\frac{345}{416}\)

\(\Leftrightarrow416\times x=13\times345\)

\(\Rightarrow416\times x=4485\)

\(\Rightarrow x=4485:416\)

\(\Rightarrow x=\frac{345}{32}\)

\(\frac{x}{13}\div\frac{15}{16}=\frac{46}{52}\)

\(\Rightarrow\frac{x}{13}\div\frac{15}{16}=\frac{23}{26}\)

\(\Rightarrow x\div13=\frac{345}{416}\)

\(\Rightarrow x=\frac{345}{52}\)

~Study well~

#Thạc_Trân

x/13+15/26=46/52

=> x/13= 46/52-15/26

=> x/13=4/13

=> x=4

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

x/13 + 15/26 = 46/52

x/13              = 46/52 - 15/26

x/13              =       4/13

=> x = 4

day la cach lam don gian va de hieu nhat

Đáp án cần chọn là: D