((5x-5)/(x+1)^2).(3+3x/20-20x)
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\(\dfrac{5x-5}{\left(x+1\right)^2}-\dfrac{20x^2-20x}{3x+3}\\ =\dfrac{5\left(x-1\right)}{\left(x+1\right)^2}-\dfrac{20x\left(x-1\right)}{3\left(x+1\right)}\\ =\dfrac{15\left(x-1\right)}{3\left(x+1\right)^2}-\dfrac{20x\left(x^2-1\right)}{3\left(x+1\right)^2}\\ =\dfrac{15x-15-20x^3+20x}{3\left(x+1\right)^2}\\ =\dfrac{-20x^3+35x-15}{3\left(x+1\right)^2}\)
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\(\dfrac{5x-5}{\left(x+1\right)^2}:\dfrac{20x^2-20}{3x+3}\\ =\dfrac{5\left(x-1\right)}{\left(x+1\right)^2}:\dfrac{20\left(x^2-1\right)}{3\left(x+1\right)}\\ =\dfrac{5\left(x-1\right)}{\left(x+1\right)^2}\cdot\dfrac{3\left(x+1\right)}{20\left(x^2-1\right)}\\ =\dfrac{3}{4\left(x+1\right)^2}\)
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a. 5x.(12x+7)-3x.(20x-5)=-150
x=-3
b. ( 2x-1).(3-x)+(x+4).(2x-5)=20
x=43/10
c. 9x2-1+(3x-1)2=0
x=1/3
d. 3x.(x-2)-(3x+2).(x-1)=7
x=-5/2
e. (2x-1)2-(2x+5).(2x-5)=20
x=3/2
f. 4x2-5=4
x=3/2
~~~~~~~~~~~ai đi ngang qua nhớ để lại k ~~~~~~~~~~~~~
~~~~~~~~~~~~ Chúc bạn sớm kiếm được nhiều điểm hỏi đáp ~~~~~~~~~~~~~~~~~~~
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a) 6x(5x + 3) + 3x(1 – 10x) = 7
⇒ 30x2+18x+3x-30x2=7
⇒21x=7
⇒x=\(\dfrac{7}{21}\)
⇒x= \(\dfrac{1}{3}\)
b) (3x – 3)(5 – 21x) + (7x + 4)(9x – 5) = 44
⇒15x-63x2-15+63x + 63x2-35x+36x-20=44
⇒79x-35=44
⇒79x=44+35
⇒79x=79
⇒x=1
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d: ta có: \(x^2-4x+4=9\left(x-2\right)\)
\(\Leftrightarrow\left(x-2\right)\left(x-11\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=11\end{matrix}\right.\)
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a) Thay x = 4 vào biểu thức A :
A = 45 - 5.44+ 5.43 - 5.42 + 5.4 -1
= 3
b) Thay x = 21 vào B :
B = 216 - 20.215 - 20.214 -20.213 - 20.212 - 20.21+3
=24
A= \(\frac{5x-5}{\left(x+1\right)^2}.\left(\frac{3+3x}{20-20x}\right)\left(\text{Đ}K\text{XĐ}:x\ne\pm1\right)\)
\(=\frac{5\left(x-1\right)}{\left(x+1\right)^2}.\frac{3\left(x+1\right)}{20\left(1-x\right)}=\frac{-3}{4\left(x+1\right)}\)
Vậy với \(x\ne\pm1\) thì A= \(\frac{-3}{4\left(x+1\right)}\)