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Bài 1
a, 32.(-64) - 64. 68
= -64.(32 + 68)
= -64 .100
= - 6400
b, -54.76 + 12.(-76) - 76.34
= -76.(54 + 12 + 34)
= -76.100
= -7600
19- 42.(-19) + 38.5
= 19 + 42.19 + 19.2.5
= 19.(1 + 42 + 10)
= 19.53
= 1007
B1 a A = 2/3+1/6-1/2=5/6-1/2=2/6=1/3
b B=3.{5.[(25+8):11]-16}+2015=3.{5.[33:11]-16}=3.{5.3-16}+2015
=3.{15-16}+2015=3.(-1)+2015=-3+2015=2012
B2 8.6+288 :(x-3)2=50
8.6+288:(x-3)=50:2
8.6+288:(x-3)=25
288:(x-3)=25-8.6
288:(x-3)=-23
x-3=-23.288
X-3=-6624
x=-6624+3
X=-6627
bai 1: a) \(A=\frac{2}{3}+\frac{5}{6}:5-\frac{1}{18}.\left(-3\right)^2\)
\(A=\frac{2}{3}+\frac{1}{6}-\frac{1}{18}.9\)
\(A=\frac{4}{6}+\frac{1}{6}-\frac{1}{2}\)
\(A=\frac{5}{6}-\frac{3}{6}\)
\(A=\frac{2}{6}=\frac{1}{3}\)
b) \(B=3\left\{5.\left[\left(5^2+2^3\right):11\right]-16\right\}+2015\)
\(B=3\left\{5.\left[\left(25+8\right):11\right]-16\right\}+2015\)
\(B=3\left\{5.\left[33:11\right]-16\right\}+2015\)
\(B=3\left\{5.3-16\right\}+2015\)
\(B=3\left\{15-16\right\}+2015\)
\(B=3.\left(-1\right)+2015\)
\(B=-3+2015\)
\(B=2012\)
bai 2: \(6.8+288:\left(x-3\right).2=50\)
\(48+288:\left(x-3\right).2=50\)
\(288:\left(x-3\right).2=50-48\)
\(288:\left(x-3\right).2=2\)
\(\left(x-3\right).2=288:2\)
\(\left(x-3\right).2=144\)
\(x-3=144:2\)
\(x-3=72\)
\(x=75\)
vay \(x=75\)
128 - 3.95 - 2\(x\) = 107
128 - 285 - 2\(x\) =107
-157 - 2\(x\) = 107
2\(x\) = -107 - 157
2\(x\) = -264
\(x\) = -264 : 2
\(x\) = -132
b, (3\(x\) - 25) - (\(x\) - 9) = 2 - \(x\)
3\(x\) - 25 - \(x\) + 9 = 2 - \(x\)
3\(x\) - \(x\) + \(x\) = 2 + 25 - 9
3\(x\) = 18
\(x\) = 18 : 3
\(x\) = 6
b: \(\Leftrightarrow x+8\in\left\{1;-1;5;-5\right\}\)
hay \(x\in\left\{-7;-9;-3;-13\right\}\)
Bài 2:
\(\left|x\right|\le13\)
\(\Rightarrow\left|x\right|\in\left\{0;1;2;...;13\right\}\)
Mà \(x\in Z\)nên \(x\in\left\{-13;-12;...;13\right\}\)
Bài 1:
b) Ta có:
\(x-5\)là ước của \(3x+2\)
\(\Rightarrow3x+2⋮x-5\)
\(\Rightarrow\left(3x-15+17\right)⋮x-5\)
Mà \(3x-15⋮x-5\Rightarrow17⋮x-5\Rightarrow x-5\inƯ\left(17\right)=\left\{1;-1;17;-17\right\}\)
+) \(x-5=1\Leftrightarrow x=6\)
+) \(x-5=-1\Leftrightarrow x=4\)
+) \(x-5=17\Leftrightarrow x=22\)
+) \(x-5=-17\Leftrightarrow x=-12\)
Vậy \(x\in\left\{6;4;22;-12\right\}\)
Ta có: \(2016:\left[25-\left(3x+2\right)\right]=32\cdot7\)
\(\Leftrightarrow25-\left(3x+2\right)=9\)
\(\Leftrightarrow3x+2=16\)
\(\Leftrightarrow3x=14\)
hay \(x=\dfrac{14}{3}\)
2016 : [25 - (3x+2)]=32.7
25 - (3x+2)= 2016 : 224
25 - (3x+2)= 9
3x+2 = 16
3x=14
x=\(\dfrac{14}{3}\)