a: =>a(x+1)(x+2)+bx(x+2)+cx(x+1)=1
=>a(x^2+3x+2)+bx^2+2bx+cx^2+cx=1
=>ax^2+3ax+2a+bx^2+2bx+cx^2+cx=1
=>x^2(a+b+c)+x(3a+2b+c)+2a=1
=>a+b+c=0 và 3a+2b+c=0 và a=1/2
=>a=1/2; b+c=-1/2; 2b+c=-3/2
=>b=-1; c=1/2; a=1/2
b: =>1=(ax+b)(x-1)+c(x^2+1)
=>x^2*a-a*x+bx-b+cx^2+c=1
=>x^2(a+c)+x(-a+b)-b+c=1
=>a+c=0 và -a+b=0 và -b+c=1
=>a+b=-1 và -a+b=0 và a+c=0
=>a=-1/2; b=-1/2; c=-a=1/2
Quy đồng mẫu thức của các phân thức
1. \(\dfrac{x-y}{2x^2-4xy+2y^2};\dfrac{x+y}{2x^2+4xy+2y^2};\dfrac{1}{y^2-x^2}\)
2. \(\dfrac{1}{x^2+8x+15};\dfrac{1}{x^2+6x+9}\)
3. \(\dfrac{1}{\left(a-b\right)\left(b-c\right)};\dfrac{1}{\left(c-b\right)\left(c-a\right)};\dfrac{1}{\left(b-a\right)\left(a-c\right)}\)
Rút gọn các biểu thức sau :
A = \(2x^2\left(-3x^3+2x^2+x-1\right)+2x\left(x^2-3x+1\right)\)
B = \(2x:\dfrac{1}{2}x+x^2\)
C = \(\left[1:\left(1+x\right)+2x:\left(1-x^2\right)\right]:\left(\dfrac{1}{x}-1\right)\)
D = \(\dfrac{x^2-y^2}{x+y}.\dfrac{\left(x+y\right)^2}{x}+\dfrac{y^2}{x+y}.\dfrac{\left(x+y\right)^2}{x}\)
E = \(\dfrac{\left|x-3\right|}{x^2-9}.\left(x^2+6x+9\right)\)
F = \(\dfrac{\sqrt{x}}{\sqrt{x}-5}-\dfrac{10\sqrt{x}}{x-25}-\dfrac{5}{\sqrt{x}+5}\)
Giải phương trình:
a) \(\dfrac{1}{x-2}+3=\dfrac{x-3}{2-x}\)
b) \(\dfrac{3}{\left(x-1\right)\left(x-2\right)}+\dfrac{2}{\left(x-3\right)\left(x-1\right)}=\dfrac{1}{\left(x-2\right)\left(x-3\right)}\)
c) \(1+\dfrac{1}{x+2}=\dfrac{12}{8+x^3}\)
Câu 1:
\(C=\dfrac{1}{x+2}-\dfrac{x^3-4x}{x^2+4}\cdot\left(\dfrac{1}{x^2+4x+4}-\dfrac{1}{4-x^2}\right)\)
a) Rút gọn C
b) x bằng mấy để C = 1?
Câu 2:
\(B=\left(\dfrac{1}{\sqrt{x}-1}-\dfrac{1}{\sqrt{x}}\right):\left(\dfrac{\sqrt{x}+1}{\sqrt{x}-2}-\dfrac{\sqrt{x}+2}{\sqrt{x}-1}\right)\)
a) Rút gọn B
b) x bằng mấy để \(\left|B\right|=B\)
Câu 3: Rút gọn:
\(A=\left[\dfrac{\left(1-a\right)^2}{3a+\left(a-1\right)^2}+\dfrac{2a^2-4a-1}{a^3-1}-\dfrac{1}{1-a}\right]:\dfrac{2a}{a^3+a}\)
Rút gọn
a) \((\dfrac{2x^2+3x}{x^3+1}+\dfrac{1}{x^2-x+1}).\dfrac{x^2-x+1}{x}\)
b) \(\left(\dfrac{1}{x-1}-\dfrac{1}{x}\right):\left(\dfrac{x+1}{x-2}-\dfrac{x+2}{x-1}\right)\)
c) \(\left(\dfrac{1}{x}+\dfrac{x}{x+1}\right).\dfrac{x^2+x}{x}\)
Rút gọn:
a) A= \(\dfrac{x+y}{x-y}-\dfrac{x}{x+y}+\dfrac{2y^2}{x^2-y^2}\)
b) B= \(\dfrac{x}{x-2}-\dfrac{10}{\left(x-2\right)\left(x+3\right)}-\dfrac{x-1}{x+3}\)
c) C= \(\dfrac{1}{x-1}-\dfrac{x-1}{x^2+x+1}-\dfrac{3}{x^3-1}\)
Bài 1: a;b;c > 0
Chứng minh : \(\dfrac{a}{3a+b+c}+\dfrac{b}{3b+a+c}+\dfrac{c}{3c+a+b}\le\dfrac{3}{5}\)
Bài 2: x;y;z \(\ne\) 1 và xyz = 1
Chứng minh : \(\dfrac{x^2}{\left(x-1\right)^2}+\dfrac{y^2}{\left(y-1\right)^2}+\dfrac{z^2}{\left(z-1\right)^2}\ge1\)
giải các phương trình sau
a, 4x- 2(1-x)= 5(x-4)
b, \(\dfrac{x}{6}+\dfrac{1-3x}{9}=\dfrac{-x+1}{12}\)
c, \(\left(x+2\right)^2-3\left(x+2\right)=0\)
d,\(\dfrac{x-5}{x}+\dfrac{x-3}{x+5}=\dfrac{x-25}{x\left(x+5\right)}\)
Rút gọn:
a) \(\dfrac{3\left(x-y\right)\left(x-z\right)^2}{6\left(x-y\right)\left(x-z\right)}\)
b) \(\dfrac{6x^2y^2}{8xy^5}\)
c) \(\dfrac{3x\left(1-x\right)}{2\left(x-1\right)}\)
d) \(\dfrac{9-\left(x+5\right)^2}{x^2+4x+4}\)
e) \(\dfrac{x^2-2x+1}{x^2-1}\)
f) \(\dfrac{8x-4}{8x^3-1}\)
g) \(\dfrac{x^2+5x+6}{x^2+4x+4}\)
k) \(\dfrac{20x^2-45}{\left(2x+3\right)^2}\)
