(4,5+36) x 2 = ?
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4,5(-x^2+16x+36)=0\(\Leftrightarrow\)-4,5x^2+72x+162=0
\(\Leftrightarrow\)-4,5x^2+81x-9x+162=0 \(\Leftrightarrow\)(x-18)(x+2)=0\(\Leftrightarrow\)x1=18 ,x2=-2
b, ( 4,5 .x 16 - 1,7 ) : ( 4,5 x 15 + 2,8 - 4,5)
( 4,5 x16 - 1,7) : ( 4,5 x 15 - 1,7 ) = 1
\(\Leftrightarrow36\left(x+6\right)+36\left(x-6\right)=\dfrac{9}{2}\left(x^2-36\right)\)
\(\Leftrightarrow x^2\cdot\dfrac{9}{2}-162-72x=0\)
\(\Leftrightarrow9x^2-144x-324=0\)
\(\Leftrightarrow x^2-16x-36=0\)
=>(x-18)(x+2)=0
=>x=18 hoặc x=-2
ĐKXĐ:\(x\ne\pm6\)
\(\dfrac{36}{x-6}+\dfrac{36}{x+6}=4,5\\ \Leftrightarrow36\left(\dfrac{1}{x-6}+\dfrac{1}{x+6}\right)=4,5\\ \Leftrightarrow\dfrac{x+6}{\left(x-6\right)\left(x+6\right)}+\dfrac{x-6}{\left(x-6\right)\left(x+6\right)}=\dfrac{1}{8}\\ \Leftrightarrow\dfrac{x+6+x-6}{x^2-36}=\dfrac{1}{8}\\ \Leftrightarrow\dfrac{2x}{x^2-36}=\dfrac{1}{8}\\ \Leftrightarrow x^2-36=16x\\ \Leftrightarrow x^2-16x-36=0\\ \Leftrightarrow\left(x^2+2x\right)-\left(18x+36\right)=0\\ \Leftrightarrow x\left(x+2\right)-18\left(x+2\right)=0\\ \Leftrightarrow\left(x+2\right)\left(x-18\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-2\left(tm\right)\\x=18\left(tm\right)\end{matrix}\right.\)
\(\dfrac{36}{x+6}+\dfrac{36}{x-6}=4,5\)
\(\Leftrightarrow36\left(x-6\right)+36\left(x+6\right)=4,5\left(x^2-36\right)\)
\(\Leftrightarrow36x-216+36x+216=4,5x^2-162\)
\(\Leftrightarrow-4,5x^2+72x+162=0\)
\(\Leftrightarrow\left(x-18\right)\left(-4,5x-9\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=18\\x=-2\end{matrix}\right.\)
bạn làm rõ hơn ở chỗ này đc ko, mk ko hiểu
⇔−4,5x2+72x+162=0⇔−4,5x2+72x+162=0
⇔(x−18)(−4,5x−9)=0
\(\frac{36}{x+6}+\frac{36}{x-6}=\) \(4,5\)\(\left(ĐKCĐ:x\ne\pm6\right)\)
\(\Leftrightarrow\frac{36\left(x-6\right)}{\left(x+6\right)\left(x-6\right)}+\frac{36\left(x+6\right)}{\left(x+6\right)\left(x-6\right)}\)\(=\frac{4,5\left(x-6\right)\left(x+6\right)}{\left(x-6\right)\left(x+6\right)}\)
\(\Leftrightarrow\frac{36x-216}{\left(x-6\right)\left(x+6\right)}+\frac{36x+216}{\left(x-6\right)\left(x+6\right)}\)\(=\frac{4,5x^2-162}{\left(x-6\right)\left(x+6\right)}\)
\(\Rightarrow36x-216+36x+216=4,5x^2-162\)
( đến đây giải phương trình ra rồi đối chiếu đkxđ là xong )
\(\frac{36}{x+6}+\frac{36}{x-6}=4,5\)
\(\frac{36}{x+6}+\frac{36}{x-6}=\frac{4,5\left(x+6\right)\left(x-6\right)}{\left(x+6\right)\left(x-6\right)}\)
\(DKXD:\hept{\begin{cases}x+6\ne0\\x-6\ne0\\\left(x+6\right)\left(x-6\right)\ne0\end{cases}}\Leftrightarrow\hept{\begin{cases}x\ne-6\\x\ne6\end{cases}}\)
\(\frac{72x}{\left(x+6\right)\left(x-6\right)}=\frac{4,5\left(x+6\right)\left(x-6\right)}{\left(x+6\right)\left(x-6\right)}\)
\(4,5x^2+72x-162=0\)
\(4,5x^2-9x+81x-162=0\)
\(4,5\left(x-2\right)+81\left(x-2\right)=0\)
\(\left(x-2\right)\left(4,5x-81\right)=0\)
\(\left(x-2\right)4,5\left(x-18\right)=0\)
\(\hept{\begin{cases}x-2=0\\x-18=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=2\\x=18\end{cases}}\)
\(a,x\times7,2+4,5\times x=17,55\)
\(x\times\left(7,2+4,5\right)=17,55\)
\(x\times11,7=17,55\)
\(x=17,55:11,7\)
\(x=1,5\)
\(b,x:0,25+x\times11=36\)
\(x\times4+x\times11=36\)
\(x\times\left(4+11\right)=36\)
\(x\times15=36\)
\(x=36:15\)
\(x=2,4\)
a: =>11,7x=17,55
=>x=1,5
b: =>x*4+x*11=36
=>15x=36
=>x=2,4
a) 12,3 : x - 4,5 : x = 15
(12,3 - 4,5) : x = 15
7,8 : x = 15
x = 7,8 : 15 = 0,52
b) 36 + X x 2,5 = 65,25
X x 2,5 = 65,25 - 36
X x 2,5 = 29,25
X = 29,25 : 2,5 = 11,7
Lần sau chép đề đầy đủ hơn nhé, HT
b,
= (4,5 x16 - 1,7) : (4,5 x 15 - 1,7)
= 1
c,
= ( 82 - 82 ) : 36 x ( 32 + 17 + 99 - 81 + 1 )
= 0 : 36 x ( 32 + 17 + 99 - 81 + 1 )
= 0 x ( 32 + 17 + 99 - 81 + 1 )
= 0
d,
= (30 : 7,5 + 0,5 x 3 - 1,5) x (4,5 - 4,5)
= (30 : 7,5 + 0,5 x 3 - 1,5) x 0
= 0
\((4,5+36)\times2\\=40,5\times2\\=81\)
= 40,5 x 2
= 81