Tìm x ∈ ℕ , biết:
a ) − 8 3 + − 1 3 < x < − 2 7 + 9 7 b ) − 5 8 + 7 2 + 23 − 8 < x < − 1 3 + 1 + 7 3 c ) − 5 4 + 19 12 + − 10 3 < x < − 19 6 + 15 2 + 11 3
Tìm x ∈ ℕ biết:
8x = 64
x =
Tìm x ∈ ℕ biết:
x3 = 343
x =
Ta có: 8x = 64
=> x = 2
Ta có: x3 = 343
=> x =7
Tìm x ∈ ℕ biết:
8x = 1
x =
8x = 1
=> x = 0
Vậy: x = 0
phonex_07(phone_07) đúng rồi mà
Bg
8x = 1
8x = 80
x = 0
Bài 1:
a) Tìm x,y \(_{\in}\) \(ℕ\) , tìm xy - 2x + 2y = 10
b) Tìm số dư của A : 4, biết:
A = 1 + 3 + 3\(^2\) + 3\(^3\) + ... + 3\(^{2023}\)
Bài 1 :
a) \(xy-2x+2y=10\)
\(\Leftrightarrow x\left(y-2\right)+2y=10\)
\(\Leftrightarrow x\left(y-2\right)+2y-4=6\)
\(\Leftrightarrow x\left(y-2\right)+2\left(y-2\right)=6\)
\(\Leftrightarrow\left(x+2\right)\left(y-2\right)=6\)
Ta có : \(x+2\ge2\) vì \(x\in N\)
Do đó : ta có bảng :
x+2 : 2 3 6
y-2 : 3 2 1
x : 0 1 4
y : 5 4 3
Vậy...........
a) \(xy-2x+2y=10\left(x;y\inℕ\right)\)
\(\Rightarrow2xy-4x+4y=20\)
\(\Rightarrow2x\left(y-2\right)+4y-8+8=20\)
\(\Rightarrow2x\left(y-2\right)+4\left(y-2\right)=12\)
\(\Rightarrow\left(2x+4\right)\left(y-2\right)=12\)
\(\Rightarrow\left(2x+4\right);\left(y-2\right)\in\left\{1;2;3;4;6;12\right\}\)
\(\Rightarrow\left(x;y\right)\in\left\{\left(-\dfrac{3}{2};14\right);\left(-1;8\right);\left(-\dfrac{1}{3};6\right);\left(0;5\right);\left(1;3\right);\left(4;3\right)\right\}\)
\(\Rightarrow\left(x;y\right)\in\left\{\left(0;5\right);\left(1;3\right);\left(4;3\right)\right\}\left(x;y\inℕ\right)\)
Tìm x ∈ ℕ biết: 3x = 9
Tìm x\(\in\)\(ℕ\) biết:
(1+x)+(2+x)+...+(100+x)=5750
( x+1) + (x+2) + (x+3) +...+ ( x+100) = 5750
<=> ( x + x + x + ...... + x ) + (1 + 2 + 3 + ..... + 100) = 5750
<=> 100x + 5050 = 5750
=> 100x = 5750 - 5050
=> 100x = 700
=> x = 700 : 100
=> x = 7
Tìm x ∈ ℕ , biết:
a ) 1 2 + − 1 3 + − 2 3 ≤ x < − 3 5 + 1 6 + − 2 5 + 3 2 b ) − 3 8 + − 18 21 + − 1 7 < x ≤ − 1 6 + 8 17 + 5 − 6 + 9 17 + 1
a ) − 1 2 ≤ x < 2 3 = > x = 0. b ) − 1 < x ≤ 1 = > x ∈ {0;1}
Tìm x ∈ ℕ , biết:
a ) − 2 5 + 1 6 + − 1 5 ≤ x < − 3 4 + 9 7 + − 1 4 + 5 7 b ) 5 17 + − 4 9 + 12 17 < x ≤ − 3 7 + 7 15 + 4 − 7 + 8 15 + 9 3
a ) − 13 30 ≤ x < 1 = > x = 0. b ) 5 9 < x ≤ 3 = > x ∈ {1;2;3}
Tìm x ∈ ℕ , biết:
a ) 11 8 + − 5 8 < x < − 3 4 + 15 4 b ) 31 23 + − 7 32 + − 8 23 < x < − 8 45 + 5 + − 37 45 c ) − 7 2 + 1 10 + − 8 5 < x < 1 12 + − 5 6 + − 5 4
a) - 2 < x < 3 = > x ∈ {0;1;2}
b) 25 32 < x < 4 => x ∈ {1;2;3}
c) – 5 < x < - 2 = > x = ∅
Tìm x ∈ ℕ , biết:
a ) 5 6 + 1 6 ≤ x ≤ 13 4 + 14 8 b ) − 5 6 + 8 3 + 29 − 6 ≤ x ≤ − 1 2 + 2 + 5 2 c ) 79 15 + 7 5 + − 8 3 ≤ x ≤ 10 3 + 15 4 + 23 12
a) 1 ≤ x ≤ 5 => x ∈ {1;2;3;4;5}
b) -3 ≤ x ≤ 4 =>x ∈ {0;1;2;3;4}
c) 4 ≤ x ≤ 9 => x ∈ {4;5;6;7;8;9}