Rút gọn phân thức :
a) \(\dfrac{12x^3y^2}{18xy^5}\)
b) \(\dfrac{15x\left(x+5\right)^3}{20x^2\left(x+5\right)}\)
Rút gọn các phân thức:
a)\(\dfrac{14xy^5\left(2x-3y\right)}{21x^2y\left(2x-3y\right)^2}\) b)\(\dfrac{8xy\left(3x-1\right)^3}{12x^3\left(1-3x\right)}\)
c) \(\dfrac{20x^2-45
}{\left(2x+3\right)^2}\) d) \(\dfrac{5x^2-10xy}{2\left(2y-x\right)^3}\)
\(a,=\dfrac{2y^4}{3x\left(2x-3y\right)}\\ b,=-\dfrac{2y\left(3x-1\right)^2}{3x^2}\\ c,=\dfrac{5\left(4x^2-9\right)}{\left(2x+3\right)^2}=\dfrac{5\left(2x-3\right)\left(2x+3\right)}{\left(2x+3\right)^2}=\dfrac{5\left(2x-3\right)}{2x+3}\\ d,=\dfrac{5x\left(x-2y\right)}{-2\left(x-2y\right)^3}=-\dfrac{5x}{2\left(x-2y\right)^2}\)
Câu 2 Rút gọn các phân thức sau::(2 điểm )
a/ \(\dfrac{21x^2y^3}{24x^3y^2}\) b/ \(\dfrac{15xy^3\left(x^2-y^2\right)}{20x^2y\left(x+y\right)^2}\)
\(a,\dfrac{21x^2y^3}{24x^3y^2}=\dfrac{7y}{8x}\)
\(b,\dfrac{15xy^3\left(x^2-y^2\right)}{20x^2y\left(x+y\right)^2}=\dfrac{15xy^3\left(x-y\right)\left(x+y\right)}{20x^2y\left(x+y\right)^2}=\dfrac{3y^2\left(x-y\right)}{4x\left(x+y\right)}=\dfrac{3xy^2-3y^3}{4x^2+4xy}\)
a) Ta có: \(\dfrac{21x^2y^3}{24x^3y^2}\)
\(=\dfrac{21x^2y^3:3x^2y^2}{24x^3y^2:3x^2y^2}\)
\(=\dfrac{7y}{8x}\)
bài 1. rút gọn phân thức sau :
a, \(\dfrac{15xy}{10x^2y}\)
b, \(\dfrac{4\left(2-x\right)}{6x\left(x-2\right)}\)
c, \(\dfrac{12x^3\left(x-4\right)^2}{8x^2\left(4-x\right)}\)
d, \(\dfrac{6x\left(x+5\right)^3}{2x^2\left(x+5\right)}\)
bài 2. rút gọn phân thức sau :
a, \(\dfrac{15\left(x-3\right)^3}{9-3x}\)
b, \(\dfrac{4\left(5x-1\right)^3}{2-10x}\)
c,\(\dfrac{9x^2y}{-15x^3y}\)
d, \(\dfrac{-15x\left(x-y\right)^2}{6x^2\left(x-y\right)^3}\)
bài 3. rút gọn phân thức sau :
a, \(\dfrac{5x^2+10x+5}{11x+11}\)
b, \(\dfrac{18x+6x^2+2x^3}{x^3-27}\)
c, \(\dfrac{12x^2+12x+3}{4x^2-1}\)
bài 4 : rút gọ phân thức đại số
A= \(\dfrac{12xy^2}{-9x^3y}\)
B=\(\dfrac{35xy\left(x-4\right)^2}{28x^2\left(4-x\right)}\)
C= \(\dfrac{6x+18y}{x^2-9y^2}\)
Bài 1:
a) \(\dfrac{15xy}{10x^2y}\)
= \(\dfrac{3.5xy}{2.5xyx}\)
= \(\dfrac{3}{2x}\)
d) \(\dfrac{6x\left(x+5\right)^3}{2x^2\left(x+5\right)}\)
= \(\dfrac{3.2x\left(x+5\right)\left(x+5\right)^2}{x.2x\left(x+5\right)}\)
= \(\dfrac{3\left(x+5\right)^2}{x}\)
Bài 2:
c) \(\dfrac{9x^2y}{-15x^3y}\)
= -\(\dfrac{3.3x^2y}{5.3x^2yx}\)
= -\(\dfrac{3}{5x}\)
d) \(\dfrac{-15x\left(x-y\right)^2}{6x^2\left(x-y\right)^3}\)
= \(\dfrac{5.3x\left(x-y\right)^2}{2x.3x\left(x-y\right)^2\left(x-y\right)}\)
= \(\dfrac{5}{2x\left(x-y\right)}\)
= \(\dfrac{5}{2x^2-2xy}\)
Rút gọn các phân thức :
a) \(\dfrac{14xy^5\left(2x-3y\right)}{21x^2y\left(2x-3y\right)^2}\)
b) \(\dfrac{8xy\left(3x-1\right)^3}{12x^3\left(1-3x\right)}\)
c) \(\dfrac{20x^2-45}{\left(2x+3\right)^2}\)
d) \(\dfrac{5x^2-10xy}{2\left(2y-x\right)^3}\)
e) \(\dfrac{32x-8x^2+2x^3}{x^3+64}\)
f) \(\dfrac{9-\left(x+5\right)^2}{x^2+4x+4}\)
g) \(\dfrac{80x^3-125x}{3\left(x-3\right)-\left(x-3\right)\left(8-4x\right)}\)
h) \(\dfrac{5x^3+5x}{x^4-1}\)
i) \(\dfrac{x^2+5x+6}{x^2+4x+4}\)
1. Rút gọn phân thức \(\dfrac{15-5x}{5x^2-15x}\)
A. \(\dfrac{-1}{x}\) B. x C. \(\dfrac{1}{x}\) D. -x
2. Phân thức \(\dfrac{x\left(x-5\right)}{x^2+25}\) có giá trị bằng 0 khi x bằng
A. -5 B. 0 C. 0 hoặc 5 D. 5
3. Phân thức nào dưới đây có kết quả rút gọn là một hằng số
A. \(\dfrac{3x-3}{x\left(x-1\right)}\) B. \(\dfrac{x^2y}{xy}\) C. \(\dfrac{x-1}{x^2-1}\) D. \(\dfrac{2x-5}{5-2x}\)
1) \(\dfrac{15-5x}{5x^2-15x}=\dfrac{5\left(3-x\right)}{5x\left(x-3\right)}=-\dfrac{5\left(x-3\right)}{5x\left(x-3\right)}=-\dfrac{1}{x}\)
Chọn A
2) \(\dfrac{x\left(x-5\right)}{x^2+25}=\dfrac{x\left(x-5\right)}{\left(x-5\right)\left(x+5\right)}=\dfrac{x}{x+5}\)
\(A=0\Leftrightarrow\dfrac{x}{x+5}=0\Leftrightarrow x=0\)
Chọn B
3) \(\dfrac{2x-5}{5-2x}=-\dfrac{5-2x}{5-2x}=-1\)
Chọn D
quy đồng mẫu thức của các phân tử
a, \(\dfrac{2}{5x^3y};\dfrac{5}{xy^2}\)
b, \(\dfrac{3x}{x-5};\dfrac{-2}{3\left(x-5\right)}\)
c, \(\dfrac{1}{\left(x+3\right)\left(x-3\right)};\dfrac{5x}{x^2-9}\)
rút gọn các phân thức
a,\(\dfrac{7xy^3\left(x-2y\right)}{14x^2y^2\left(x-2y\right)^2}\)
b,\(\dfrac{4a^2-8ab}{2\left(2b-a\right)^3}\)
c,\(\dfrac{3x^3-3x}{x^4-1}\)
d,\(\dfrac{45x\left(3-x\right)}{15x\left(x-3\right)^3}\)
c: \(=\dfrac{3x\left(x-1\right)\left(x+1\right)}{\left(x-1\right)\left(x+1\right)\left(x^2+1\right)}=\dfrac{3x}{x^2+1}\)
\(\dfrac{15x\left(x+5\right)}{20x^2\left(x+5\right)}\)
\(\dfrac{x^3-4x^2}{y\left(x-4\right)}\)
\(\dfrac{5\left(a-2c\right)^2}{2a^2-4ac}\)
(*)\(\dfrac{15x\left(x+5\right)}{20x^2\left(x+5\right)}=\dfrac{3}{4x}\)
(*)\(\dfrac{x^3-4x^2}{y\left(x-4\right)}=\dfrac{x^2\left(x-4\right)}{y\left(x-4\right)}=\dfrac{x^2}{y}\)
(*)\(\dfrac{5\left(a-2c\right)^2}{2a^2-4ac}=\dfrac{5\left(a-2c\right)^2}{2a\left(a-2c\right)}=\dfrac{5\left(a-2c\right)}{2a}\)
Làm phép tính nhân phân thức :
a) \(\dfrac{30x^3}{11y^2}.\dfrac{121y^5}{25x}\)
b) \(\dfrac{24y^5}{7x^2}.\left(-\dfrac{21x}{12y^3}\right)\)
c) \(\left(-\dfrac{18y^3}{25x^4}\right).\left(-\dfrac{15x^2}{9y^3}\right)\)
d) \(\dfrac{4x+8}{\left(x-10\right)^3}.\dfrac{2x-20}{\left(x+2\right)^2}\)
e) \(\dfrac{2x^2-20x+50}{3x+3}.\dfrac{x^2-1}{4\left(x-5\right)^3}\)