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\(\dfrac{3}{4}\left(x^2y\right)^2:\dfrac{1}{8}xy^2\\ =\dfrac{3}{4}x^4y^2:\dfrac{1}{8}xy^2\\ =\left(\dfrac{3}{4}:\dfrac{1}{8}\right)\left(x^4:x\right)\left(y^2:y^2\right)\\ =6x^3\)
\(\dfrac{3}{4}\left(x^2y\right)^2\div\dfrac{1}{8}xy^2\)
\(=\dfrac{3}{4}x^4y^2\div\dfrac{1}{8}xy^2\)
\(=6x^3\)
a: \(P=\dfrac{8}{x\left(x+4\right)}+\dfrac{5x}{x\left(x+4\right)}-\dfrac{2x+8}{x\left(x+4\right)}=\dfrac{8+5x-2x-8}{x\left(x+4\right)}=\dfrac{3}{x+4}\)
b: Thay x=1/2 vào P, ta được:
P=3:9/2=3x2/9=6/9=2/3
Với khác 0 ; x khác 4
\(P=\dfrac{8+5x-2x-8}{x\left(x+4\right)}=\dfrac{3x}{x\left(x+4\right)}=\dfrac{3}{x+4}\)
Thay x = 1/2 vào P ta được \(\dfrac{3}{\dfrac{1}{2}+4}=\dfrac{3}{\dfrac{9}{2}}=3:\dfrac{9}{2}=\dfrac{2}{3}\)
\(<=>2x^2-5x+3=0\)
<=>\(2x^2-2x-3x+3=0\)
\(<=>2x(x-1)-3(x-1)=0\)
\(<=>(2x-3)(x-1)=0\)
th1 \(2x-3=0<=>x=3/2\)
th2 \(X-1=0<=>x=1\)
pt có tập nghiệm S={3/2;1}
\(2x^3+3x^2-8x+3=0\\ \Rightarrow\left(2x^3-2x^2\right)+\left(5x^2-5x\right)-\left(3x-3\right)=0\\ \Rightarrow2x^2\left(x-1\right)+5x\left(x-1\right)-3\left(x-1\right)=0\\ \Rightarrow\left(x-1\right)\left(2x^2+5x-3\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-1=0\\2x^2+5x-3=0\end{matrix}\right.\)
\(x-1=0\\ \Rightarrow x=1\)
\(2x^2+5x-3=0\\ \Rightarrow\left(2x^2+6x\right)-\left(x+3\right)=0\\ \Rightarrow2x\left(x+3\right)-\left(x+3\right)=0\\ \Rightarrow\left(x+3\right)\left(2x-1\right)=0\\ \Rightarrow\left[{}\begin{matrix}x+3=0\\2x-1=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=-3\\x=\dfrac{1}{2}\end{matrix}\right.\)
Vậy \(x=\left\{-3;\dfrac{1}{2};1\right\}\)
Bài 6
\(a,ĐK:x\ne\pm5\\ b,P=\dfrac{x-5+2x+10-2x-10}{\left(x-5\right)\left(x+5\right)}=\dfrac{x-5}{\left(x-5\right)\left(x+5\right)}=\dfrac{1}{x+5}\\ c,P=-3\Leftrightarrow\dfrac{1}{x+5}=-3\Leftrightarrow-3\left(x+5\right)=1\Leftrightarrow x=-\dfrac{16}{3}\\ \Leftrightarrow Q=\left(3x-7\right)^2=\left[3\cdot\left(-\dfrac{16}{3}\right)-7\right]^2=529\)
Bài 7:
\(a,ĐK:x\ne\pm3\\ b,P=\dfrac{3x-9+x+3+18}{\left(x-3\right)\left(x+3\right)}=\dfrac{4\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{4}{x-3}\\ b,P=4\Leftrightarrow4\left(x-3\right)=4\Leftrightarrow x=4\)
b)\(3x\left(x+3y\right)-6xy\left(x+3y\right)\)
\(=\left(3x-6xy\right)\left(x+3y\right)\)
c)\(x\left(x+y\right)-5x-5y\)
\(=x\left(x+y\right)-5\left(x+y\right)\)
\(=\left(x-5\right)\left(x+y\right)\)
Bài 1:
b. \(3x\left(x+3y\right)-6xy\left(x+3y\right)\)
= (3x - 6xy)(x + 3y)
= 3x(1 - 2y)(x + 3y)
c. \(x\left(x+y\right)-5x-5y\)
= x(x + y) - 5(x + y)
= (x - 5)(x + y)
d. \(3\left(x-y\right)-5x\left(y-x\right)\)
= 3(x - y) + 5x(x - y)
= (3 + 5x)(x - y)
Bài 3:
a. x + 6x2 = 0
<=> x(1 + 6x) = 0
<=> \(\left[{}\begin{matrix}x=0\\1+6x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{-1}{6}\end{matrix}\right.\)
b. 2(x + 3) - x(x + 3) = 0
<=> (2 - x)(x + 3) = 0
<=> \(\left[{}\begin{matrix}2-x=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)
c. 5x(x - 2) - (2 - x) = 0
<=> 5x(x - 2) + (x - 2) = 0
<=> (5x + 1)(x - 2) = 0
<=> \(\left[{}\begin{matrix}5x+1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{5}\\x=2\end{matrix}\right.\)
d. (x + 1) = (x + 1)2
<=> (x + 1) - (x + 1)2 = 0
<=> (1 - x - 1)(x + 1) = 0
<=> -x(x + 1) = 0
<=> \(\left[{}\begin{matrix}-x=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)