B.1:Tìm x
A)x-2=-6+17
B)x+2=-9-11
C)/x-4/=-81
D)/x-5/=(x-4)²
B.2:Tìm x € Z
A)19 :"dấu chia hết nhé"(x-2)
B) x-7:"DCHN"x+4
Giúp em nhanh nhá mn sáng maj pải nộp ùi
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Bài 1:
a: \(\Leftrightarrow x-1\in\left\{1;-1;3;-3\right\}\)
hay \(x\in\left\{2;0;4;-2\right\}\)
câu 1:
a) 500-(300)-190+(-210)
= 500-300-190-210
= 200 - 210 -190
=-10 - 190
=-200
b) (-3)3 .5+12.(-6)
= -27.5 -72
=-135 - 72
=-207
c) 15.(-19-4)-19.(15-4)
= 15.(-23) - 19.11
=-345 - 209
=-554
câu 2: tìm x thuộc Z
a) 3x-2=3
=> 3x=3/2
=> x=1/2
b) x chia hết cho 5 và -7<x<11
=> x thuộc {-5;0;5;10}
Câu 1:
a) Ta có: \(500-\left(300\right)-190+\left(-210\right)\)
\(=500-300-190-210\)
\(=\left(500-300\right)-\left(190+210\right)\)
\(=200-400=-200\)
b) Ta có: \(\left(-3\right)^3\cdot5+12\cdot\left(-6\right)\)
\(=\left(-3\right)^3\cdot5-3\cdot4\cdot3\cdot2\)
\(=-5\cdot3^3-3^2\cdot8\)
\(=3^2\cdot\left(-5\cdot3-8\right)\)
\(=9\cdot\left(-15-8\right)=9\cdot\left(-23\right)=-207\)
c) Ta có: \(15\cdot\left(-19-4\right)-19\cdot\left(15-4\right)\)
\(=-15\cdot19-15\cdot4-15\cdot19+19\cdot4\)
\(=-30\cdot19+4\cdot4\)
\(=-2\cdot\left(15\cdot19+2\cdot4\right)\)
\(=-2\cdot\left(285+8\right)=-586\)
a: Bạn ghi lại đề nha bạn
b: \(30\left(x+2\right)-6\left(x-5\right)-24x=100\)
=>\(30x+60-6x+30-24x=100\)
=>\(\left(30x-6x-24x\right)+\left(60+30\right)=100\)
=>0x=100-90=10(vô lý)
c: \(\left(x-7\right)\left(x+3\right)< 0\)
TH1: \(\left\{{}\begin{matrix}x-7>0\\x+3< 0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x>7\\x< -3\end{matrix}\right.\)
=>\(x\in\varnothing\)
TH2: \(\left\{{}\begin{matrix}x-7< 0\\x+3>0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x< 7\\x>-3\end{matrix}\right.\)
=>-3<x<7
mà x nguyên
nên \(x\in\left\{-2;-1;0;1;2;3;4;5;6\right\}\)
d: -1<2x-1<4
=>\(-1+1< 2x< 4+1\)
=>0<2x<5
=>0<x<2,5
mà x nguyên
nên \(x\in\left\{1;2\right\}\)
a) 2(x + 3) = 5(1 - x) - 2
<=> 2x + 6 = 5 - 5x - 2
<=> 2x + 6 = 3 - 5x
=> 2x - 5x = 6 + 3
=> -3x = 9
=> x = 9 : (-3)
=> x = -3
\(a,x+\dfrac{2}{5}=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}-\dfrac{2}{5}\)
\(x=\dfrac{5}{10}-\dfrac{4}{10}\)
\(\Rightarrow x=....\)
\(a,x+\dfrac{2}{5}=\dfrac{1}{2}\\ \Rightarrow x=\dfrac{1}{2}-\dfrac{2}{5}=\dfrac{5-4}{10}=\dfrac{1}{10}\)
\(b,x-\dfrac{2}{5}=\dfrac{1}{7}\\ \Rightarrow x=\dfrac{1}{7}+\dfrac{2}{5}=\dfrac{5+14}{35}=\dfrac{19}{35}\)
\(c,x\cdot\dfrac{3}{4}=\dfrac{9}{20}\\ \Rightarrow x=\dfrac{9}{20}:\dfrac{3}{4}=\dfrac{9}{20}\cdot\dfrac{4}{3}=\dfrac{3\cdot1}{5\cdot1}=\dfrac{3}{5}\)
\(d,x:\dfrac{1}{7}=14\\ \Rightarrow x=14\cdot\dfrac{1}{7}=\dfrac{14}{7}=2\)
\(e,\dfrac{2}{3}-x=\dfrac{1}{5}\\ \Rightarrow x=\dfrac{2}{3}-\dfrac{1}{5}=\dfrac{10-3}{15}=\dfrac{7}{15}\)
\(f,\dfrac{4}{15}:x=\dfrac{12}{25}\\ \Rightarrow x=\dfrac{4}{15}:\dfrac{12}{25}=\dfrac{4}{15}\cdot\dfrac{25}{12}=\dfrac{1\cdot5}{3\cdot3}=\dfrac{5}{9}\)
\(7^6+7^5-7^4\)
\(=7^4\left(7^2+7-1\right)\)
\(=7^4\cdot55⋮55\)
\(16^5+2^5\)
\(=\left(2^4\right)^5+2^5\)
\(=2^{20}+2^5\)
\(=2^5\left(2^{15}+1\right)\)
\(=2^5\cdot32769⋮33\)
a. \(\left(x^2-2x+1\right)-3x\left(x-1\right)=0\)
\(\Leftrightarrow x^2-2x+1-3x^2+3x=0\)
\(\Leftrightarrow-2x^2+x+1=0\)
\(\Leftrightarrow-2x^2+2x-x+1=0\)
\(\Leftrightarrow-2x\left(x-1\right)-\left(x-1\right)=0\)
\(\Leftrightarrow-\left(2x+1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x+1=0\\x-1=0\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}x=-\frac{1}{2}\\x=1\end{cases}}\)
Vậy \(x\in\left\{-\frac{1}{2};1\right\}\)
b. \(4\left(7x-3\right)-\left(7x^2-3x\right)=0\)
\(\Leftrightarrow4\left(7x-3\right)-x\left(7x-3\right)=0\)
\(\Leftrightarrow\left(4-x\right)\left(7x-3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}4-x=0\\7x-3=0\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}x=4\\x=\frac{3}{7}\end{cases}}\)
Vậy \(x\in\left\{4;\frac{3}{7}\right\}\)
c.\(\left(5-x\right)\left(2+3x\right)=4-9x^2\)
\(\Leftrightarrow\left(5-x\right)\left(2+3x\right)=\left(2-3x\right)\left(2+3x\right)\)
\(\Leftrightarrow\left(2+3x\right)\left(5-x-2+3x\right)=0\)
\(\Leftrightarrow\left(2+3x\right)\left(2x+3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2+3x=0\\2x+3=0\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}x=-\frac{2}{3}\\x=-\frac{3}{2}\end{cases}}\)
Vậy \(x\in\left\{-\frac{2}{3};-\frac{3}{2}\right\}\)
d. \(7-\left(2x+4\right)=-\left(x+4\right)\)
\(\Leftrightarrow7-2x-4=-x-4\)
\(\Leftrightarrow7-4+4=-x+2x\)
\(\Leftrightarrow7=x\)
Vậy x = 7
e. \(\left(x-1\right)-\left(2x-1\right)=9\)
\(\Leftrightarrow x-1-2x+1=9\)
\(\Leftrightarrow-x=9\)
\(\Leftrightarrow x=-9\)
g. \(x^3+x^2+x+1=0\)
\(\Leftrightarrow x^2\left(x+1\right)+\left(x+1\right)=0\)
\(\Leftrightarrow\left(x^2+1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x^2+1=0\\x+1=0\end{cases}}\)Mà : \(x^2+1\ge1>0\)
\(\Leftrightarrow x+1=0\)
\(\Leftrightarrow x=-1\)
Vậy x = -1
Làm tạm cách này ko suy ra luôn cũng đc.
a) x2-3 chia hết cho x-1
Ta có:
x2-3=x(x-1)+x-3
=>x-3 chia hết cho x-1
=>x-1-2 chia hết cho x-1
=>2 chia hết cho x-1
=>x-1 thuộc Ư(2)
=>Ư(2)={-1;1;-2;2}
Ta có bảng sau:
x-1 | -1 | 1 | -2 | 2 |
x | 0 | 2 | -1 | 3 |
NX | tm | tm | loại | tm |
Vậy...
b) x2+3x-5 chia hết cho x-2
Ta có:
x2+3x-5=x2-2x+5x-10+5
=x(x-2)+5(x-2)+5
=(x-2)(x+5)+5
=>5 chia cho x-2
=>x-2 thuộc Ư(5)
=>Ư(5)={-1;1;-5;5}
Ta có bảng sau:
x-2 | -1 | 1 | -5 | 5 |
x | 1 | 3 | -3 | 7 |
NX | tm | tm | loại | tm |
Vậy...
c) x2-3x+1 chia hết cho x+2
Ta có:
x2-3x+1=x2+2x-5x-10+11
=x(x+2)-5(x+2)+11
=>(x+2)(x-5)+11
=>11 chia hết cho x+2
=>x+2 thuộc Ư(11)
=>Ư(11)={-1;1;-11;11}
=> Làm tương tự hai câu trên