Rút gọn
\(\frac{1}{(a+b)^3}(\frac{1}{a^3}+\frac{1}{b^3})+\frac{3}{(a+b)^4}(\frac{1}{a^2}+\frac{1}{b^2})+ \frac{6}{(a+b)^5}(\frac{1}{a}+\frac{1}{b})\)
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
H9
HT.Phong (9A5)
CTVHS
18 tháng 8 2023
a) \(a^{\dfrac{1}{3}}\cdot a^{\dfrac{1}{2}}\cdot a^{\dfrac{7}{6}}=a^{\dfrac{1}{3}+\dfrac{1}{2}+\dfrac{7}{6}}=a^2\)
b) \(a^{\dfrac{2}{3}}\cdot a^{\dfrac{1}{4}}:a^{\dfrac{1}{6}}=a^{\dfrac{2}{3}+\dfrac{1}{4}-\dfrac{1}{6}}=a^{\dfrac{3}{4}}\)
c) \(\left(\dfrac{3}{2}a^{-\dfrac{3}{2}}\cdot b^{-\dfrac{1}{2}}\right)\left(-\dfrac{1}{3}a^{\dfrac{1}{2}}b^{\dfrac{2}{3}}\right)=\left(\dfrac{3}{2}\cdot-\dfrac{1}{3}\right)\left(a^{-\dfrac{3}{2}}\cdot a^{\dfrac{1}{2}}\right)\left(b^{-\dfrac{1}{2}}\cdot b^{\dfrac{2}{3}}\right)\)
\(=-\dfrac{1}{2}a^{-1}b^{-\dfrac{1}{3}}\)
10 tháng 5 2016
\(D=\left(\frac{a-b}{a^{\frac{3}{4}}+a^{\frac{1}{2}}.b^{\frac{1}{4}}}-\frac{a^{\frac{1}{2}}-b^{\frac{1}{2}}}{a^{\frac{1}{4}}+b^{\frac{1}{4}}}\right):\left(a^{\frac{1}{4}}-b^{\frac{1}{4}}\right)^{-1}\sqrt{\frac{a}{b}}\)
\(=\left[\frac{a-b}{a^{\frac{1}{2}}\left(a^{\frac{1}{4}}+b^{\frac{1}{4}}\right)}-\frac{a^{\frac{1}{2}}-b^{\frac{1}{2}}}{a^{\frac{1}{4}}+b^{\frac{1}{4}}}\right]:\left(a^{\frac{1}{4}}-b^{\frac{1}{4}}\right)^{-1}\sqrt{\frac{b}{a}}\)
\(=\frac{a-b-a+a^{\frac{1}{2}}.b^{\frac{1}{2}}}{a^{\frac{1}{2}}\left(a^{\frac{1}{4}}+b^{\frac{1}{4}}\right)}.\frac{1}{\left(a^{\frac{1}{4}}-b^{\frac{1}{4}}\right)}=\frac{b^{\frac{1}{2}}}{a^{\frac{1}{2}}}\frac{\left(a^{\frac{1}{4}}-b^{\frac{1}{4}}\right)}{\left(a^{\frac{1}{4}}-b^{\frac{1}{4}}\right)}\sqrt{\frac{a}{b}}.\sqrt{\frac{a}{b}}=1\)
23 tháng 3 2017
Ta có:
\(A=\frac{1}{\left(x+y\right)^3}\left(\frac{1}{x^4}-\frac{1}{y^4}\right)=\frac{1}{\left(x+y\right)^3}.\frac{\left(y^2+x^2\right)\left(x+y\right)\left(y-x\right)}{x^4y^4}=\frac{\left(x^2+y^2\right)\left(y-x\right)}{\left(x+y\right)^2x^4y^4}\)
\(B=\frac{1}{\left(x+y\right)^4}.\left(\frac{1}{x^3}-\frac{1}{y^3}\right)=\frac{\left(y-x\right)\left(y^2+xy+x^2\right)}{\left(x+y\right)^4x^3y^3}\)
\(C=\frac{1}{\left(x+y\right)^5}\left(\frac{1}{x^2}-\frac{1}{y^2}\right)=\frac{y-x}{\left(x+y\right)^4x^2y^2}\)
\(\Rightarrow A+B+C=\frac{\left(x^2+y^2\right)\left(y-x\right)}{\left(x+y\right)^2x^4y^4}+\frac{\left(y-x\right)\left(x^2+xy+y^2\right)}{\left(x+y\right)^4x^3y^3}+\frac{\left(y-x\right)}{\left(x+y\right)^4x^2y^2}\)
\(=\frac{y^3-x^3}{x^4y^4\left(x+y\right)^2}\)
b/ Thế vô rồi tính nhé
23 tháng 3 2017
Đoạn gần cuối thay y-x= 1 luôn
\(A+B+C=\frac{x^2+y^2}{\left(x+y\right)^2x^4y^4}+\left(\frac{\left(x+y\right)^2}{\left(x+y\right)^4\left(xy\right)^3}\right)\\ \)
\(A+B+C=\frac{x^2+y^2}{\left(x+y\right)^2\left(xy\right)^4}+\frac{1}{\left(x+y\right)^2\left(xy\right)^3}\)
\(A+B+C=\frac{x^2+y^2+xy}{\left[\left(x+y\right)xy\right]^2\left(xy\right)^2}\) giờ mới thay không biết đã tối giản chưa
3 tháng 10 2016
Đặt \(a+b=x\) , \(ab=y\)
Ta có biểu thức cần rút gọn :
\(\frac{1}{x^3}.\frac{x\left(x^2-3y\right)}{y^3}+\frac{3}{x^4}.\frac{x^2-2y}{y^2}+\frac{6}{x^5}.\frac{x}{y}=\frac{x^4-3x^2y+3yx^2-6y^2+6y^2}{x^4y^3}=\frac{x^4}{x^4y^3}=\frac{1}{y^3}=\frac{1}{a^3b^3}\)
\(\dfrac{1}{\left(a+b\right)^3}\left(\dfrac{1}{a^3}+\dfrac{1}{a^3}\right)+\dfrac{3}{\left(a+b\right)^4}+\left(\dfrac{1}{a^2}+\dfrac{1}{b^2}\right)+\dfrac{6}{\left(a+b\right)^5}\left(\dfrac{1}{a}+\dfrac{1}{b}\right)\)
\(=\dfrac{1}{\left(a+b\right)^3}\cdot\dfrac{b^3+a^3}{a^3b^3}+\dfrac{3}{\left(a+b\right)^4}\cdot\dfrac{b^2+a^2}{a^2b^2}+\dfrac{6}{\left(a+b\right)^5}\cdot\dfrac{b+a}{ab}\)
\(=\dfrac{1}{\left(a+b\right)^3}\cdot\dfrac{\left(b+a\right)\left(a^2-ab+a^2\right)}{a^3b^3}+\dfrac{3\left(b^2+a^2\right)}{a^2b^2\cdot\left(a+b\right)^4}\cdot\dfrac{6}{\left(a+b\right)^4}\cdot\dfrac{1}{ab}\)
\(=\dfrac{1}{\left(a+b\right)^2}\cdot\dfrac{b^2-ab+a^2}{a^3b^3}+\dfrac{3b^2+3a^2}{a^2b^2\cdot\left(a+b\right)^4}+\dfrac{6}{ab\left(a+b\right)^4}\)
\(=\dfrac{b^2-ab+a^2}{a^3b^3\cdot\left(a+b\right)^2}+\dfrac{3b^2+3a^2}{a^2b^2\cdot\left(a+b\right)^4}+\dfrac{6}{ab\cdot\left(a+b\right)^4}\)
\(=\dfrac{\left(a+b\right)^2\cdot\left(b^2-ab+a^2\right)+ab\left(3b^2+3a^2\right)+6a^2b^2}{a^3b^3\cdot\left(a+b\right)^4}\)
\(=\dfrac{\left(a^2+2ab+b^2\right)\left(b^2-ab+a^2\right)+3ab^3+3a^3b+6a^2b^2}{a^3b^3\cdot\left(a+b\right)^4}\)
\(=\dfrac{a^2b^2-a^3b+a^4+2ab^3-2a^2b^2+2a^3b+b^4-ab^3+a^2b^2+3ab^3+3a^2b+6a^2b^2}{a^3b^3\cdot\left(a+b\right)^4}\)
\(=\dfrac{6a^2b^2+4a^3b+a^4+4ab^3+b^4}{a^3b^3\cdot\left(a+b\right)^4}\)