Lê Đình Đức
Giới thiệu về bản thân
a: ĐKXĐ: \(x \notin \left{\right. 1 ; - 1 ; \frac{1}{2} \left.\right}\)
\(A = \left(\right. \frac{1}{1 - x} + \frac{2}{x + 1} - \frac{5 - x}{1 - x^{2}} \left.\right) : \frac{1 - 2 x}{x^{2} - 1}\)
\(= \left(\right. \frac{- 1}{x - 1} + \frac{2}{x + 1} - \frac{x - 5}{\left(\right. x - 1 \left.\right) \left(\right. x + 1 \left.\right)} \left.\right) \cdot \frac{\left(\right. x - 1 \left.\right) \left(\right. x + 1 \left.\right)}{- 2 x + 1}\)
\(= \frac{- \left(\right. x + 1 \left.\right) + 2 \left(\right. x - 1 \left.\right) - x + 5}{\left(\right. x - 1 \left.\right) \left(\right. x + 1 \left.\right)} \cdot \frac{\left(\right. x - 1 \left.\right) \left(\right. x + 1 \left.\right)}{- 2 x + 1}\)
\(= \frac{- x - 1 + 2 x - 2 - x + 5}{- 2 x + 1} = \frac{2}{- 2 x + 1}\)
b: Để A>0 thì \(\frac{2}{- 2 x + 1} > 0\)
mà 2>0
nên -2x+1>0
=>-2x>-1
=>\(x < \frac{1}{2}\)
Kết hợp ĐKXĐ, ta được: \(\left{\right. x < \frac{1}{2} \\ x \neq - 1\)
a: \(x^{2} - 3 x + 1 > 2 \left(\right. x - 1 \left.\right) - x \left(\right. 3 - x \left.\right)\)
=>\(x^{2} - 3 x + 1 > 2 x - 2 - 3 x + x^{2}\)
=>-3x+1>-x-2
=>-2x>-3
=>\(x < \frac{3}{2}\)
b: \(\left(\left(\right. x - 1 \left.\right)\right)^{2} + x^{2} < = \left(\left(\right. x + 1 \left.\right)\right)^{2} + \left(\left(\right. x + 2 \left.\right)\right)^{2}\)
=>\(x^{2} - 2 x + 1 + x^{2} < = x^{2} + 2 x + 1 + x^{2} + 4 x + 4\)
=>-2x+1<=6x+5
=>-7x<=4
=>\(x > = - \frac{4}{7}\)
c:
\(\left(\right. x^{2} + 1 \left.\right) \left(\right. x - 6 \left.\right) < = \left(\left(\right. x - 2 \left.\right)\right)^{3}\)
=>\(x^{3} - 6 x^{2} + x - 6 < = x^{3} - 6 x^{2} + 12 x - 8\)
=>x-6<=12x-8
=>-11x<=-8+6=-2
=>\(x > = \frac{2}{11}\)
a: \(\frac{3 x + 5}{2} - x > = 1 + \frac{x + 2}{3}\)
=>\(\frac{3 x + 5 - 2 x}{2} > = \frac{3 + x + 2}{3}\)
=>\(\frac{x + 5}{2} - \frac{x + 5}{3} > = 0\)
=>\(\frac{3 \left(\right. x + 5 \left.\right) - 2 \left(\right. x + 5 \left.\right)}{6} > = 0\)
=>\(\frac{x + 5}{6} > = 0\)
=>x+5>=0
=>x>=-5
b: \(\frac{x - 2}{3} - x - 2 < = \frac{x - 17}{2}\)
=>\(\frac{2 \left(\right. x - 2 \left.\right)}{6} + \frac{6 \left(\right. - x - 2 \left.\right)}{6} < = \frac{3 \left(\right. x - 17 \left.\right)}{6}\)
=>\(2 \left(\right. x - 2 \left.\right) + 6 \left(\right. - x - 2 \left.\right) < = 3 \left(\right. x - 17 \left.\right)\)
=>\(2 x - 4 - 6 x - 12 < = 3 x - 51\)
=>-4x-16<=3x-51
=>-7x<=-35
=>x>=5
c: \(\frac{2 x + 1}{3} - \frac{x - 4}{4} < = \frac{3 x + 1}{6} - \frac{x - 4}{12}\)
=>\(\frac{4 \left(\right. 2 x + 1 \left.\right) - 3 \left(\right. x - 4 \left.\right)}{12} < = \frac{2 \left(\right. 3 x + 1 \left.\right) - x + 4}{12}\)
=>4(2x+1)-3(x-4)<=2(3x+1)-x+4
=>8x+4-3x+12<=6x+2-x+4
=>5x+16<=5x+6
=>16<=6(sai)
Vậy: BPT vô nghiệm
a: \(\frac{3 \left(\right. 2 x + 1 \left.\right)}{20} + 1 > \frac{3 x + 52}{10}\)
=>\(\frac{6 x + 3}{20} + \frac{20}{20} > \frac{6 x + 104}{20}\)
=>6x+23>6x+104
=>23>104(sai)
vậy: \(x \in \emptyset\)
b: \(\frac{4 x - 1}{2} + \frac{6 x - 19}{6} < = \frac{9 x - 11}{3}\)
=>\(\frac{3 \left(\right. 4 x - 1 \left.\right) + 6 x - 19}{6} < = \frac{2 \left(\right. 9 x - 11 \left.\right)}{6}\)
=>12x-3+6x-19<=18x-22
=>-22<=-22(luôn đúng)
Vậy: \(x \in R\)