Bài 6: Tìm số nguyên x, biếtA, 3 – (17 – x) = 289 – (36 + 289)B, 25 – (x + 5) = -415 – (15 – 415)C, 34 + (21 – x) = (3747 – 30) – 3746D, -2x – (x – 17) = 34 – (-x + 25)E, 17x + (-16x – 37) = 2x + 43G, (x + 12). (x – 3) = 0H, (-x + 5). (3 – x) = 0K, -28 – 7. |-3x + 15| = - 70M, 12 – 2. (-x + 3)2 = - 38N, - {-3x + 2. [45 – x – 3. (3x + 7) – 2x] + 4x} = 55Bài 7: So sánhA, (-99). 98. (-97) với 0B, (-5). (-4). (-3). (-2). (-1) với 0C, (-245)....
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Bài 6: Tìm số nguyên x, biết
A, 3 – (17 – x) = 289 – (36 + 289)
B, 25 – (x + 5) = -415 – (15 – 415)
C, 34 + (21 – x) = (3747 – 30) – 3746
D, -2x – (x – 17) = 34 – (-x + 25)
E, 17x + (-16x – 37) = 2x + 43
G, (x + 12). (x – 3) = 0
H, (-x + 5). (3 – x) = 0
K, -28 – 7. |-3x + 15| = - 70
M, 12 – 2. (-x + 3)2 = - 38
N, - {-3x + 2. [45 – x – 3. (3x + 7) – 2x] + 4x} = 55
Bài 7: So sánh
A, (-99). 98. (-97) với 0
B, (-5). (-4). (-3). (-2). (-1) với 0
C, (-245). (-47). (-199) với 123. (+315)
D, 2987. (-1974). (+243). 0 với 0
E, (-12). (-45) : (-27) với |-1|
1,
a) |x| + |y + 1| =0
Ta có: |x| \(\ge\) 0 (Với x \(\in\) Z)
|y + 1| \(\ge\) 0 (Với y\(\in\) Z)
\(\Rightarrow\) |x| + |y + 1| \(\ge\) 0
Dấu "=" xảy ra (=):
\(\left\{\begin{matrix}\left|x\right|=0\\\left|y+1\right|=0\end{matrix}\right.\Rightarrow\left\{\begin{matrix}x=0\\y+1=0\end{matrix}\right.\Rightarrow}\left\{\begin{matrix}x=0\\y=0-1\end{matrix}\right.\Rightarrow}\left\{\begin{matrix}x=0\\y=-1\end{matrix}\right.\)
Vậy x = 0; y = -1
b) (2 - x)4 = 81
\(\Rightarrow\) (2 - x)4 = 34 = (-3)4
\(\Rightarrow\) \(\left[\begin{matrix}2-x=3\\2-x=-3\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=2-3\\x=2-\left(-3\right)\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-1\\x=5\end{matrix}\right.\)
Vậy: x \(\in\) {-1; 5}
c) |x - 1| + (-3) = 17
\(\Rightarrow\) |x - 1| = 17 - (-3)
\(\Rightarrow\) |x - 1| = 20
\(\Rightarrow\left[\begin{matrix}x-1=-20\\x-1=20\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-20+1\\x=20+1\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-19\\x=21\end{matrix}\right.\)
Vậy: x \(\in\) {-19; 21}
d) 3 - (17 - x) = 289 - (36 + 289)
\(\Rightarrow\) 3 - (17 - x) = 289 - 36 - 289
\(\Rightarrow\) 3 - (17 - x) = 289 - 289 - 36\(\Rightarrow\) 3 - (17 - x) = 0 - 36
\(\Rightarrow\) 3 - (17 - x) = -36 \(\Rightarrow\) 17 - x = 3 - (-36) \(\Rightarrow\) 17 - x = 39 \(\Rightarrow\) x = 17 - 39 \(\Rightarrow\) x = -22 Vậy: x = -22 e) 25 - (x + 5) = -415 - (15 - 415) \(\Rightarrow\) 25 - (x + 5) = -415 - 15 + 415 \(\Rightarrow\) 25 - (x + 5) = (-415 + 415) - 15 \(\Rightarrow\) 25 - (x + 5) = 0 - 15 \(\Rightarrow\) 25 - (x + 5) = -15 \(\Rightarrow\) x + 5 = 25 - (-15) \(\Rightarrow\) x + 5 = 40 \(\Rightarrow\) x = 40 -5 \(\Rightarrow\) x = 35 Vậy: x = 35 f) 34 + (21 - x) = (3747 - 30) - 3746 \(\Rightarrow\) 34 + (21 - x) = 3747 - 30 - 3746 \(\Rightarrow\) 34 + (21 - x) = 3747 - 3746 - 30 \(\Rightarrow\) 34 + (21 - x) = 1 - 30 \(\Rightarrow\) 34 + (21 - x) = -29 \(\Rightarrow\) 21 - x = -29 - 34 \(\Rightarrow\) 21 - x = -63 \(\Rightarrow\) x = 21 - (-63) \(\Rightarrow\) x = 84 Vậy: x = 84Lớp 6 chưa học "BĐT" :v