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a)\(-\frac{21}{x}+\frac{18}{x}=\frac{-21+18}{x}=\frac{-3}{x}\in Z\)
=>-3 chia hết x
=>x thuộc Ư(-3)
=>x thuộc {1;-1;3;-3}
b)\(\frac{2x-5}{x+1}=\frac{2\left(x+1\right)-7}{x+1}=\frac{2\left(x+1\right)}{x+1}-\frac{7}{x+1}=2-\frac{7}{x+1}\in Z\)
=>7 chia hết x+1
=>x+1 thuộc Ư(7)
=>x+1 thuộc {1;-1;7;-7}
=>x thuộc {0;-2;6;-8}
c)\(\frac{3x+2}{x-1}-\frac{x-5}{x-1}=\frac{3x+2-\left(x-5\right)}{x-1}=\frac{2x+7}{x-1}=\frac{2\left(x-1\right)+9}{x-1}=\frac{2\left(x-1\right)}{x-1}+\frac{9}{x-1}\)\(=2+\frac{9}{x-1}\in Z\)
=>9 chia hết x-1
=>x-1 thuộc Ư(9)
=>....
Còn lại bạn tự làm típ nha khi nào ko làm đc thì nhắn vs mk :)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)\(f\left(x\right)=x^5-3x^2+7x^4-x^5+2x^2-9x^3+x^2-\frac{1}{4}x+2x-3\)
\(=x^5-x^5+7x^4-9x^3-3x^2+2x^2+x^2-\frac{1}{4}x+2x-3\)
\(=7x^4-9x^3+\frac{7}{4}x-3\)
\(g\left(x\right)=5x^4-x^5+\frac{1}{2}x^2+x^5+x^2-4x^4-2x^3+3x^2+x^3-\frac{1}{4}\)
\(=-x^5+x^5+5x^4-4x^4-2x^3+x^3+\frac{1}{2}x^2+x^2+3x^2-\frac{1}{4}\)
\(=x^4-x^3+\frac{9}{2}x^2-\frac{1}{4}\)
b)\(f\left(1\right)=7.1^4-9.1^3+\frac{7}{4}.1-3=7-9+\frac{7}{4}-3=-\frac{13}{4}\)
\(f\left(-1\right)=7.\left(-1\right)^4-9.\left(-1\right)^3+\frac{7}{4}.\left(-1\right)-3=7+9-\frac{7}{4}-3=\frac{45}{4}\)
\(g\left(1\right)=1^4-1^3+\frac{9}{2}.1^2-\frac{1}{4}=1-1+\frac{9}{2}-\frac{1}{4}=\frac{17}{4}\)
\(g\left(-1\right)=\left(-1\right)^4-\left(-1\right)^3+\frac{9}{2}.\left(-1\right)^2-\frac{1}{4}=1+1+\frac{9}{2}-\frac{1}{4}=\frac{25}{4}\)
c) Ta có: f(x)+g(x)=\(7x^4-9x^3+\frac{7}{4}x-3+x^4-x^3+\frac{9}{2}x^2-\frac{1}{4}=7x^4+x^4-9x^3-x^3+\frac{9}{2}x^2+\frac{7}{4}x-3-\frac{1}{4}\)
\(=8x^4-10x^3+\frac{9}{2}x^2+\frac{7}{4}x-\frac{13}{4}\)
f(x)-g(x) =\(7x^4-9x^3+\frac{7}{4}x-3-x^4+x^3-\frac{9}{2}x^2+\frac{1}{4}=7x^4-x^4-9x^3+x^3-\frac{9}{2}x^2+\frac{7}{4}x-3+\frac{1}{4}\)
\(=6x^4-8x^3-\frac{9}{2}x^2+\frac{7}{4}x-\frac{11}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)\(\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{7}{4}.\frac{5}{2}\)
\(\left(\frac{1}{3}.x\right):\frac{2}{3}=\frac{35}{8}\)
\(\frac{1}{3}.x=\frac{35}{8}.\frac{2}{3}\)
\(\frac{1}{3}.x=\frac{35}{12}\)
\(x=\frac{35}{12}:\frac{1}{3}\)
\(x=\frac{35}{12}.\frac{3}{1}\)
\(x=\frac{35}{4}\)
b)\(\frac{4,5}{0,3}=\frac{2,25}{0,1.x}\)
\(4,5.\left(0,1.x\right)=2,25.0,3\)
\(4,5.\left(0,1.x\right)=0,675\)
\(0,1.x=0,675:4,5\)
\(0,1.x=0,15\)
\(x=0,15:0,1\)
\(x=1.5\)
c)\(\frac{8}{\frac{1}{4}.x}=\frac{2}{0,02}\)
\(\left(\frac{1}{4}.x\right).2=8.0,02\)
\(\left(\frac{1}{4}.x\right).2=0,16\)
\(\frac{1}{4}.x=0,16:2\)
\(\frac{1}{4}.x=0,08\)
\(x=0,08:\frac{1}{4}\)
\(x=0,32\)
d)\(\frac{3}{\frac{9}{4}}=\frac{\frac{3}{4}}{6.x}\)
\(3.\left(6.x\right)=\frac{3}{4}.\frac{9}{4}\)
\(3.\left(6.x\right)=\frac{27}{16}\)
\(6.x=\frac{27}{16}:3\)
\(6.x=\frac{9}{16}\)
\(x=\frac{9}{16}:6\)
\(x=\frac{3}{32}\)
HỌC TỐT ^^
![](https://rs.olm.vn/images/avt/0.png?1311)
a) + x=1/3
A=2x2-5x+1
A=2/9-5/3+1=1/9
+ x=-1/3
A=21/9
tương tự P=3x2+5x1-1 thì x cũng có 2 gtri là +-0,5
thông cảm bn tự giải nha
kb vs mik đi
![](https://rs.olm.vn/images/avt/0.png?1311)
Noob ơi, bạn phải đưa vào máy tính ý solve cái là ra x luôn, chỉ tội là đợi hơi lâu
a, 4.(18 - 5x) - 12(3x - 7) = 15(2x - 16) - 6(x + 14)
=> 72 - 20x - 36x + 84 = 30x - 240 - 6x - 84
=> (72 + 84) + (-20x - 36x) = (30x - 6x) + (-240 - 84)
=> 156 - 56x = 24x - 324
=> 24x + 56x = 324 + 156
=> 80x = 480
=> x = 480 : 80 = 6
Vậy x = 6