a/ \(\left(P\right):3\left(x-0\right)+0\left(y-2\right)+1\left(z+5\right)=0\Rightarrow\left(P\right):3x+z+5=0\)

b/\(\overrightarrow{AB}\left(2;4;-9\right);\overrightarrow{AC}\left(4;0;-7\right)\)

 \(\overrightarrow{n_{\left(P\right)}}=\left[\overrightarrow{AB},\overrightarrow{AC}\right]=\left(4.\left(-7\right)-0.\left(-9\right);\left(-9\right).4-\left(-7\right).2;2.0-4.4\right)=\left(-28;-22;-16\right)\)

\(\Rightarrow\left(P\right):-28\left(x-0\right)-22\left(y-1\right)-16\left(z-7\right)=0\Rightarrow\left(P\right):28x+22y+16z-134=0\)

c/ Truc Oy di qua O(0;0;0) va co vtcp \(\overrightarrow{j}\left(0;1;0\right)\)

\(\overrightarrow{OD}\left(3;-6;2\right)\)

\(\Rightarrow\overrightarrow{n_{\left(P\right)}}=\left[\overrightarrow{j};\overrightarrow{OD}\right]=\left(2;0;-3\right)\)

\(\Rightarrow\left(P\right):2\left(x-0\right)+0\left(y-1\right)-3\left(z-0\right)=0\Rightarrow\left(P\right):2x-3z=0\)

d/ \(\overrightarrow{Oz}\left(0;0;1\right)\)

\(\overrightarrow{DE}\left(5;-2;-7\right)\)

\(\Rightarrow\overrightarrow{n_{\left(P\right)}}=\left[\overrightarrow{Oz};\overrightarrow{DE}\right]=\left(2;5;0\right)\)

\(\Rightarrow\left(P\right):2\left(x-0\right)+5\left(y-0\right)+0\left(z-1\right)=0\Rightarrow\left(P\right):2x+5y=0\)

e/ \(\overrightarrow{n_{Oyz}}=\overrightarrow{n_{\left(P\right)}}=\left(1;0;0\right)\)

\(\Rightarrow\left(P\right):1\left(x-3\right)=0\Rightarrow\left(P\right):x-3=0\)

f/ Cách làm giống câu b

g/ \(\overrightarrow{HI}=\overrightarrow{IK}\Rightarrow\left\{{}\begin{matrix}x_I=\dfrac{3-1}{2}=1\\y_I=\dfrac{-1+5}{2}=2\\z_1=\dfrac{2-4}{2}=-1\end{matrix}\right.\Rightarrow I\left(1;2;-1\right)\)

\(\overrightarrow{n_{\left(P\right)}}=\overrightarrow{HK}\left(-4;6;-6\right)\)

\(\Rightarrow\left(P\right):-4\left(x-1\right)+6\left(y-2\right)-6\left(z+1\right)=0\Rightarrow\left(P\right):-4x+6y-6z+2=0\)

P/s: Bạn tính toán lại kết quả hộ mình nhé !

1 Her mother is not as hospitable as her

2 Hung is fond of swimming in the summer

3 Let's travel abroad

4 There are 4 chairs in my room

5 Don't forget to drink more water

6 Minh is the most intelligent student in my class

I. \(\dfrac{3}{4}\times\dfrac{3}{4}\times\dfrac{1}{4}\times\dfrac{1}{4}\times4C2=\dfrac{27}{128}\)

II. 27/64

III. 81/256

IV.  (=II +III) 189/256

2 ý đúng

A

A

1: 

a: =-1/21-3/21=-4/21

b: =-20/36-3/36=-23/36

d: =12/3-2/3=10/3

e: =10/7-4+3/14

=20/14+3/14-4

=23/14-56/14=-33/14

2:

a: =>x-3/5=2/3

=>x=2/3+3/5=19/15

b: =>3/8-x=7/5+1/8

=>3/8-x=61/40

=>x=-23/20

d: =>-37/30-x=2

=>x=-37/30-2=-97/30

Bài này dễ thôi bạn.

Trả lời:

3x - 7 = 5

3x = 5 + 7

3x = 12

x = 12:3

x = 4

Vậy x = 4

  Ủng hộ nhé

Mình còn tưởng x là nhân cơ

3x-7=5

<=>3x=12

<=>x=4

#include <bits/stdc++.h>

using namespace std;

int n,i,x,dem;

int main()

{

cin>>n;

dem=0;

for (i=1; i<=n; i++)

{

cin>>x;

if (x%2==0) dem++;

}

cout<<dem;

return 0;

}

\(\left\{{}\begin{matrix}x_1+x_2=3\\x_1x_2=2\end{matrix}\right.\)

\(A=\dfrac{2x_1^2+2x_2^2}{x_1x_2}+\dfrac{3}{4}=\dfrac{2\left[\left(x_1+x_2\right)^2-2x_1x_2\right]}{2}+\dfrac{3}{4}\)

\(=\dfrac{2\cdot\left(3^2-2\cdot2\right)}{2}+\dfrac{3}{4}=9-4+0.75=5.75=\dfrac{23}{4}\)

Theo Vi et \(\left\{{}\begin{matrix}x_1+x_2=3\\x_1x_2=2\end{matrix}\right.\)

\(A=\dfrac{2x_1^2+2x_2^2}{x_1x_2}+\dfrac{3}{4}=\dfrac{2\left[\left(x_1+x_2\right)^2-2x_1x_2\right]}{x_1x_2}+\dfrac{3}{4}\)

Thay vào ta được \(\dfrac{2\left(9-4\right)}{2}+\dfrac{3}{4}=5+\dfrac{3}{4}=\dfrac{23}{4}\)