tim x\(\in\)N biet
107.10x+3=217.517
x2017=x
Tim x , y \(\in\)N*,biet:
x^2=1!+2!+3!+...+y!
tim x thuoc N, biet [x-1] [x+3]=6
\(\left(x-1\right)\left(x+3\right)=6\)
\(\Rightarrow6⋮\left(x-1\right),\left(x+3\right)\)
\(\Rightarrow\left(x-1\right),\left(x+3\right)\inƯ\left(6\right)\)
\(\RightarrowƯ\left(6\right)=\left\{1;2;3;6\right\}\)
Ta có bảng :
x - 1 | 1 | 2 |
x + 3 | 6 | 3 |
x | 2 | 3 |
x | 3 | 0 |
Tim x,y \(\in N\) biet 25-y2 = 8(x-2014)2
Ta co : 8(x-2014)2 = 25-y2
=> 8(x-2014)2 + y2 = 25 (*)
Voi moi \(y\in N\) ta co y2 \(\ge0\)
\(\Rightarrow8\left(x-2014\right)^2\le25\)
\(\Rightarrow\left(x-2014\right)^2\le\dfrac{25}{3}\)
Vi x\(\in N\)
\(\Rightarrow\left(x-2014\right)^2=0hoac\left(x-2014\right)^2=1\)
Neu\(\left(x-2014\right)^2=1\) thay vao(*) ta duoc;
8 . 1+ y2 =25
\(\Rightarrow25-8=y^2\)
17 = y2 (loai) (vi y \(\in N\))
Neu \(\left(x-2014\right)^2=0\) thay vao (*) ta duoc:
8 . 0 + y2 = 25
=> y2 = 25
=> y = 5 (vi y\(\in N\))
Khi do \(\left(x-2014\right)^2=0\)
=> x- 2014 = 0 => x = 2014
Vay x = 2014, y = 5
Tim x thuoc N biet
( x - 2 ) ^2016 + ( x -3 ) = 3
Đặt \(A=\left(x-2\right)^{2016}+\left(x-3\right)\)
\(x-2< 2\) vì nếu \(x-2\ge2\)
\(\Rightarrow x-3\ge1\)
\(\left(x-2\right)^{2016}>3\)
\(\Rightarrow A=\left(x-2\right)^{2016}+\left(x-3\right)>3\) ( vô lý )
\(\Rightarrow x-2< 2\)
\(\Rightarrow x< 4\)
Với \(x=0\)
\(\Rightarrow A=\left(x-2\right)^{2016}+\left(x-3\right)=2^{2016}-3>3\)
Với \(x=1\)
\(\Rightarrow A=\left(x-2\right)^{2016}+\left(x-3\right)< 0< 3\)
Với \(x=2\)
\(\Rightarrow A=\left(x-2\right)^{2016}+\left(x-3\right)=0-1< 3\)
Với \(x=3\)
\(\Rightarrow A=\left(x-2\right)^{2016}+\left(x-3\right)=1+0< 3\)
Do đó không có \(x\in N\) thỏa mãn.
tim x,y thuoc N* biet 1+x+x^2+x^3=2^y
tim x y e n biet
( x - 4 ). ( x - 3 ) =0
( x - 4 ) . ( x - 3 ) = 0
Mà một số nhân với 0 = 0
\(\Rightarrow\)1 trong hay vế phải bằng 0
Nếu x = 4
\(\left(4-4\right).\left(4-3\right)=0.1=0\)
Nếu x = 3
\(\left(3-4\right).\left(3-3\right)=-1.0=0\)
\(\Rightarrow x=3;4\)
th1: x- 4= 0 th2: x-3= 0
x= 0+4 x= 0+3
x= 4 x=3
tim x,y thuoc N biet (x-6).(2y+3)=8
Tim x;y thuoc N biet (x-1)(2y+3)=26
\(\left(x-1\right)\left(2y+3\right)=1\cdot26=26\cdot1=2\cdot13=13\cdot2\)
Ta co bang sau:
x-1 | 1 | 26 | 2 | 13 | ||||
2y+3 | 26 | 1 | 13 | 2 | ||||
x | 2 | 27 | 3 | 14 | ||||
y | 11.5 (loai) | -1(loai) | 5 | -0.5(loai) |