2^x+3=35
(x+1)^2=16
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\(A=\dfrac{1}{5}\left(\dfrac{1}{6}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{16}+...+\dfrac{1}{496}-\dfrac{1}{501}\right)\)
\(=\dfrac{1}{5}\cdot\dfrac{55}{334}=\dfrac{11}{334}\)
\(B=1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{19}-\dfrac{1}{21}=\dfrac{20}{21}\)
1:
=>2x-3=0 hoặc 5/2-x=0
=>x=3/2 hoặc x=5/2
2: =>x=1/2+12=12,5
3: =>(2x+3/5-3/5)(2x+3/5+3/5)=0
=>2x(2x+6/5)=0
=>x=0 hoặc x=-3/5
4: =>-1/6x=-1/3
=>x=1/3:1/6=2
5: =>1/4:x=1/4
=>x=1
6: =>2/5x+11/15=1
=>2/5x=4/15
=>x=2/3
Lời giải:
a. $\frac{2-x}{4}=\frac{3x-1}{3}$
$\Rightarrow 3(2-x)=4(3x-1)$
$\Rightarrow 6-3x=12x-4$
$\Rightarrow 6+4=12x+3x$
$\Rightarrow 10=15x$
$\Rightarrow x=\frac{10}{15}=\frac{2}{3}$
b.
$\frac{x}{7}=\frac{x+16}{35}$
$\Rightarrow \frac{5x}{35}=\frac{x+16}{35}$
$\Rightarrow 5x=x+16$
$\Rightarrow 4x=16$
$\Rightarrow x=4$
c.
$\sqrt{x^2+1}=3$
$\Rightarrow x^2+1=9$
$\Rightarrow x^2=8\Rightarrow x=\pm \sqrt{8}=\pm 2\sqrt{2}$
\(\dfrac{45}{135}=\dfrac{45:45}{135:45}=\dfrac{1}{3}\)
\(\dfrac{117}{234}=\dfrac{117:117}{234:117}=\dfrac{1}{2}\)
\(\dfrac{1515}{2727}=\dfrac{1515:303}{2727:303}=\dfrac{5}{9}\)
\(\dfrac{232323}{494949}=\dfrac{232323:10101}{494949:10101}=\dfrac{23}{49}\)
\(\left(x-\dfrac{1}{3}\right)+\dfrac{1}{4}=\dfrac{1}{2}\)
\(x-\dfrac{1}{3}=\dfrac{1}{2}-\dfrac{1}{4}\)
\(x-\dfrac{1}{3}=\dfrac{2}{4}-\dfrac{1}{4}\)
\(x-\dfrac{1}{3}=\dfrac{1}{4}\)
\(x=\dfrac{1}{4}+\dfrac{1}{3}\)
\(x=\dfrac{3}{12}+\dfrac{4}{12}\)
\(x=\dfrac{7}{12}\)
\(x-\left(\dfrac{1}{7}+\dfrac{2}{5}\right)=\dfrac{16}{35}\)
\(x-\left(\dfrac{5}{35}+\dfrac{14}{35}\right)=\dfrac{16}{35}\)
\(x-\dfrac{19}{35}=\dfrac{16}{35}\)
\(x=\dfrac{16}{35}+\dfrac{19}{35}\)
\(x=\dfrac{35}{35}\)
\(x=1\)
\(x+\dfrac{3}{7}=\dfrac{2}{5}+\dfrac{3}{10}\)
\(x+\dfrac{3}{7}=\dfrac{4}{10}+\dfrac{3}{10}\)
\(x+\dfrac{3}{7}=\dfrac{7}{10}\)
\(x=\dfrac{7}{10}-\dfrac{3}{7}\)
\(x=\dfrac{49}{70}-\dfrac{30}{70}\)
\(x=\dfrac{19}{30}\)
ĐKXĐ: \(x\ne-1;\) \(x\ne-3;\)\(x\ne-5;\)\(x\ne-7\)
\(\frac{1}{x^2+4x+3}+\frac{1}{x^2+8x+15}+\frac{1}{x^2+12x+35}=\frac{3}{16}\)
\(\Leftrightarrow\)\(\frac{1}{\left(x+1\right)\left(x+3\right)}+\frac{1}{\left(x+3\right)\left(x+5\right)}+\frac{1}{\left(x+5\right)\left(x+7\right)}=\frac{3}{16}\)
\(\Leftrightarrow\)\(\frac{1}{2}\left(\frac{1}{x+1}-\frac{1}{x+3}+\frac{1}{x+3}-\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+7}\right)=\frac{3}{16}\)
\(\Leftrightarrow\)\(\frac{1}{x+1}-\frac{1}{x+7}=\frac{3}{8}\)
\(\Leftrightarrow\)\(\frac{6}{\left(x+1\right)\left(x+7\right)}=\frac{3}{8}\)
\(\Rightarrow\)\(3\left(x+1\right)\left(x+7\right)=48\)
\(\Leftrightarrow\)\(x^2+8x+7=16\)
\(\Leftrightarrow\)\(x^2+8x-9=0\)
\(\Leftrightarrow\)\(\left(x+1\right)\left(x-9\right)=0\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}x=-1\left(KTMĐKXĐ\right)\\x=9\left(TMĐKXĐ\right)\end{cases}}\)
Vậy...
\(\frac{1}{x^2+4x+3}+\frac{1}{x^2+8x+15}+\frac{1}{x^2+12x+35}=\frac{3}{16}\)
\(\Leftrightarrow\frac{1}{x^2+x+3x+3}+\frac{1}{x^2+3x+5x+15}+\frac{1}{x^2+5x+7x+35}=\frac{3}{16}\)
\(\Leftrightarrow\frac{1}{\left(x+1\right)\left(x+3\right)}+\frac{1}{\left(x+3\right)\left(x+5\right)}+\frac{1}{\left(x+5\right)\left(x+7\right)}=\frac{3}{16}\)
\(\Leftrightarrow\frac{\left(x+5\right)\left(x+7\right)}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)}+\frac{\left(x+1\right)\left(x+7\right)}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)}+\frac{\left(x+1\right)\left(x+3\right)}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)}\)
\(=\frac{3\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)}\)
Mẫu của mỗi phân thức bằng nhau nên => tử của mỗi phân thức cũng phải bằng nhau
=> Đến đây thì dễ rồi, bạn giải ra tìm x
1).( 27,56 x 35 ) + ( 27,56 x 67 ) - ( 27,56 x 2)
= (964 + 1846,52) - 55,12
=2810,52 - 55,12
= 2755,4
2).( 4x 35 ) x ( 25 x 5 ) x 2
= ( 140 x 125 ) x2
= 17500 x 2
=35000
4). 3/10
5). 1188
6). 61/6
e: =>3x-6=12x-4
=>-9x=2
=>x=-2/9
f: =>5x=x+16
=>4x=16
=>x=4
a: Ta có: \(\sqrt{x}< 3\)
nên \(0\le x< 9\)
b: Ta có: \(\sqrt{4x+16}+\sqrt{x+4}+2\sqrt{9x+36}=35\)
\(\Leftrightarrow2\sqrt{x+4}+\sqrt{x+4}+6\sqrt{x+4}=35\)
\(\Leftrightarrow\sqrt{x+4}=\dfrac{35}{9}\)
\(\Leftrightarrow x+4=\dfrac{1225}{81}\)
hay \(x=\dfrac{901}{81}\)
a) \(\sqrt{x}< 3\Rightarrow x< 9\)
b) \(\sqrt{4x+16}+\sqrt{x+4}+2\sqrt{9x+36}=35\)
\(\Rightarrow2\sqrt{x+4}+\sqrt{x+4}+6\sqrt{x+4}=35\)
\(\Rightarrow\sqrt{x+4}=\dfrac{35}{9}\)
\(\Rightarrow x+4=\dfrac{1225}{81}\)
\(\Rightarrow x=\dfrac{901}{81}\)
c) \(\sqrt{x+2\sqrt{x-1}}=3\)
\(\Rightarrow\sqrt{\left(x-1\right)+2\sqrt{x-1}+1}=3\)
\(\Rightarrow\sqrt{\left(x-1+1\right)^2}=3\)
\(\Rightarrow\sqrt{x^2}=3\)
\(\Rightarrow\left|x\right|=3\) \(\Rightarrow\left\{{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)
2x + 3 = 35
2x = 32 = 25
=> x = 5
b) (x+1)2 = 16 = 42 = (-4)2
=> x + 1 = 4 => x = 3
x + 1 = -4 => x = -5
KL:..