Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Lời giải:
a)
\(|x|=2019\Rightarrow \left[\begin{matrix} x=2019\\ x=-2019\end{matrix}\right.\)
b)
\(|x-3|=21\Rightarrow \left[\begin{matrix} x-3=21\\ x-3=-21\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=24\\ x=-18\end{matrix}\right.\)
c)
\(|x|-25+x=9\)
\(\Leftrightarrow |x|+x=34\)
Nếu $x\geq 0$: $|x|=x$
\(\Rightarrow x+x=34\Rightarrow 2x=34\Rightarrow x=17\) (thỏa mãn)
Nếu $x< 0$: $|x|=-x$
$\Rightarrow -x+x=34\Rightarrow 0=34$ (vô lý -loại)
Vậy $x=17$
d) \(|x-2|+2x=4\)
Nếu $x\geq 2\Rightarrow |x-2|=x-2$
$\Rightarrow x-2+2x=4\Rightarrow 3x=6\Rightarrow x=2$ (thỏa mãn)
Nếu $x< 2\Rightarrow |x-2|=2-x$
$\Rightarrow 2-x+2x=4\Rightarrow x=2$ (loại vì $x< 2$)
Vậy $x=2$
e)
$|x-5|+3x+2=13$
Nếu $x\geq 5$ thì $|x-5|=x-5$
\(\Rightarrow x-5+3x+2=13\)
\(\Leftrightarrow 4x=16\Leftrightarrow x=4\) (loại vì $x\geq 5$)
Nếu $x< 5$ thì $|x-5|=5-x$
$\Rightarrow 5-x+3x+2=13$
$\Leftrightarrow 2x=6\Rightarrow x=3$ (thỏa mãn)
Vậy $x=3$
\(a,2\frac{x}{7}=\frac{75}{35}\)
\(\frac{75}{35}=2\frac{5}{35}=2\frac{1}{7}\)
\(\Rightarrow x=1\)
\(b,47:4=...\left(+3\right)\)
\(\Rightarrow\left(47-3\right):4=11\)
\(\Rightarrow x=11\)
\(c,\frac{112}{5}=\frac{336}{15}=22\left(+6\right)\)
\(\Rightarrow x=22\frac{x=6}{15}\)
\(d,7,5x=\frac{75x}{100}:\left(9-6\frac{13}{21}\right)=2\frac{13}{25}\)
\(\frac{75x}{100}:\left(9-\frac{139}{21}\right)=\frac{63}{25}\)
\(\frac{75x}{100}:\frac{50}{21}=\frac{63}{25}\)
\(\Rightarrow\frac{63^3}{25^{\left(1\right)}}\cdot\frac{50^{\left(2\right)}}{21^1}=6=\frac{6}{1}\)
\(\Rightarrow\frac{6}{1}=\frac{600}{100}\)
Con d sai đề
a/ => (x2 - 5)(x + 5)(x - 5) = 0
=> x2 - 5 = 0 => x2 = 5 => x = \(+-\sqrt{5}\) (loại)
hoặc x + 5 = 0 => x = -5
hoặc x - 5 = 0 => x = 5
Vậy x = 5 ; x = -5
b/ => x + 5 = 0 => x = -5
hoặc 9 + x2 = 0 => x2 = -9 (vô nghiệm)
Vậy x = -5
c/ => x + 3 = 0 => x = -3
hoặc x2 + 1 = 0 => x2 = -1 (vô nghiệm)
Vậy x = -3
d/ => (x + 5)(x + 2)(x - 2) = 0
=> x + 5 = 0 => x = -5
hoặc x + 2 = 0 => x = -2
hoặc x - 2 = 0 => x = 2
Vậy x = -5 ; x = -2; x = 2
a) \(\left(x^2-5\right)\left(x^2-25\right)< 0\)
Vì \(x^2-5>x^2-25\) nên \(\left\{{}\begin{matrix}x^2-5>0\\x^2-25< 0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x^2>5\\x^2< 25\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\sqrt{5}< x< -\sqrt{5}\left(vl\right)\\-5< x< 5\end{matrix}\right.\)
b) \(\left(x+5\right)\left(9+x^2\right)< 0\)
Vì \(9+x^2>0\) nên \(x+5< 0\Leftrightarrow x< -5\)
c) \(\left(x+3\right)\left(x^2+1\right)=0\)
Vì \(x^2+1>0\) nên \(x+3=0\Leftrightarrow x=-3\)
d) \(\left(x+5\right)\left(x^2-4\right)=0\)
\(\Rightarrow\left(x+5\right)\left(x+2\right)\left(x-2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-5\\x=-2\\x=2\end{matrix}\right.\)
a, <=>(-5)x=(-5)3
<=> x=3
b, <=> 52x=522
<=> x=11
c, 32x=317.315
<=> 32x=332
<=> x=16
d,2x+1=225
<=> x+1=25
<=> x=24
Chúc hok tốt!!!
a,|x|+3=5
\(\Leftrightarrow\left|x\right|=5-3=2\)
\(\Rightarrow x=\left\{{}\begin{matrix}2\\-2\end{matrix}\right.\)
b,|x+3|=5
\(\Rightarrow\left\{{}\begin{matrix}x+3=5\\x+3=-5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2\\-8\end{matrix}\right.\)
c,|x-7|+13=25
<=>|x-7|=25-13=12
\(\Rightarrow\left\{{}\begin{matrix}x-7=12\\x-7=-12\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=19\\x=-5\end{matrix}\right.\)
d,\(26-\left|x+9\right|=-13\)
\(\Leftrightarrow\left|x+9\right|=26-\left(-13\right)=39\)
\(\Rightarrow\left\{{}\begin{matrix}x+9=39\\x+9=-39\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=30\\x=-48\end{matrix}\right.\)
e,8-|x|=15
<=>|x|=8-15=-7
\(\Rightarrow\left\{{}\begin{matrix}x=-7\\x=7\end{matrix}\right.\)
f,6-|-3+x|=-15
\(\Leftrightarrow\left|-3+x\right|=6-\left(-15\right)=21\)
\(\Rightarrow\left\{{}\begin{matrix}-3+x=21\\-3+x=-21\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=24\\x=-18\end{matrix}\right.\)
a, |x| + 3 = 5
|x| = 5 - 3
|x| = 2
|x| = 2 hoặc |x| = -2
Vậy |x| thuộc {2; -2}
b,|x + 3| = 5
|x + 3| = 5 hoặc |x + 3| = -5
x = 5 - 3 x = (-5) - 3
x = 2 x = -8
Vậy x thuộc {2; -8}
c,|x - 7| + 13 = 25
|x - 7| = 25 - 13
|x - 7| = 12
|x - 7| = 12 hoặc |x - 7| = -12
x = 12 + 7 x = (-12) + 7
x = 19 x = -5
Vậy x thuộc {19 ; -5}
Bài 1:
a) \(\frac{25}{4}+\frac{-5}{4}=\frac{25-5}{4}=\frac{20}{4}=5\)
b)\(\frac{-5}{9}+\left(\frac{-2}{7}\right)=\frac{-35}{63}+\left(\frac{-18}{63}\right)=\frac{-53}{63}\)
c) \(\frac{1}{4}+\frac{9}{11}+\frac{7}{4}+\left(\frac{-2}{11}\right)=\left(\frac{1}{4}+\frac{7}{4}\right)+\left(\frac{-2}{11}+\frac{9}{11}\right)=2+\frac{7}{11}=\frac{22+7}{11}=\frac{29}{11}\)
d) \(\frac{-5}{19}.\frac{8}{19}+\left(\frac{-14}{19}\right).\frac{11}{19}=\frac{-40}{361}-\frac{151}{361}=-\frac{191}{361}\)
Bài 2:
a) \(x+\frac{5}{9}=\frac{-8}{9}\) \(\Leftrightarrow x=\frac{-8}{9}-\frac{5}{9}\) \(\Leftrightarrow x=-\frac{13}{9}\)
b) \(\frac{-1}{8}-x=\frac{9}{20}\) \(\Leftrightarrow x=\frac{-1}{8}-\frac{9}{20}\) \(\Leftrightarrow x=\frac{-5}{40}-\frac{18}{40}\) \(\Leftrightarrow x=-\frac{23}{40}\)
c) (x + 5)3 - 12 = 15
\(\Leftrightarrow\)(x + 5)3 = 27
\(\Leftrightarrow\)x + 5 = 3
\(\Leftrightarrow\)x = -2
d) \(\left|x-3\right|-\frac{4}{15}=\frac{26}{15}\) \(\Leftrightarrow\left|x-3\right|=2\) \(\Leftrightarrow\orbr{\begin{cases}x-3=2\\x-3=-2\end{cases}}\) \(\Leftrightarrow\orbr{\begin{cases}x=5\\x=1\end{cases}}\)
Đáp án là C
Ta có: 25.x = -225
⇔ x = -225 : 25
⇔ x = -9