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k: \(\left(4x-16\right)\left(-72+9x\right)=0\)
=>\(4\cdot\left(x-4\right)\cdot9\left(x-8\right)=0\)
=>\(36\left(x-4\right)\left(x-8\right)=0\)
=>\(\left(x-4\right)\left(x-8\right)=0\)
=>\(\left[{}\begin{matrix}x-4=0\\x-8=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=8\end{matrix}\right.\)
m: \(\left(20+5x\right)\left(4x-8\right)=0\)
=>\(5\cdot\left(x+4\right)\cdot4\left(x-2\right)=0\)
=>\(\left(x+4\right)\left(x-2\right)=0\)
=>\(\left[{}\begin{matrix}x+4=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=2\end{matrix}\right.\)
n: \(\left(-4x+48\right)\left(2x-24\right)=0\)
=>\(-4\left(x-12\right)\cdot2\left(x-12\right)=0\)
=>\(\left(x-12\right)^2=0\)
=>x-12=0
=>x=12
o: \(\left(4x+16\right)\left(-2x+20\right)\left(-40+x\right)=0\)
=>\(4\cdot\left(x+4\right)\cdot\left(-2\right)\left(x-10\right)\left(x-40\right)=0\)
=>\(\left(x+4\right)\left(x-10\right)\left(x-40\right)=0\)
=>\(\left[{}\begin{matrix}x+4=0\\x-10=0\\x-40=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=10\\x=40\end{matrix}\right.\)
p: \(\left(-5x+40\right)\left(-x+2023\right)\left(2x-2\right)=0\)
=>\(-5\left(x-8\right)\cdot\left(-1\right)\cdot\left(x-2023\right)\cdot2\left(x-1\right)=0\)
=>\(\left(x-8\right)\left(x-2023\right)\left(x-1\right)=0\)
=>\(\left[{}\begin{matrix}x-8=0\\x-1=0\\x-2023=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=1\\x=2023\end{matrix}\right.\)
q: \(2024x\left(4x-8\right)\left(5+5x\right)=0\)
=>\(x\cdot4\left(x-2\right)\cdot5\left(x+1\right)=0\)
=>\(x\left(x-2\right)\left(x+1\right)=0\)
=>\(\left[{}\begin{matrix}x=0\\x-2=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-1\end{matrix}\right.\)
r: \(-4x\left(3x+9\right)\left(2x-16\right)=0\)
=>\(-4x\cdot3\left(x+3\right)\cdot2\left(x-8\right)=0\)
=>\(x\left(x+3\right)\left(x-8\right)=0\)
=>\(\left[{}\begin{matrix}x=0\\x+3=0\\x-8=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-3\\x=8\end{matrix}\right.\)
s: \(\left(-100+5x\right)\left(2x-10\right)\left(6x+6\right)=0\)
=>\(5\cdot\left(x-20\right)\cdot2\left(x-5\right)\cdot6\left(x+1\right)=0\)
=>\(\left(x-20\right)\left(x-5\right)\left(x+1\right)=0\)
=>\(\left[{}\begin{matrix}x-20=0\\x-5=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=20\\x=5\\x=-1\end{matrix}\right.\)
t: \(\left(-2x+4\right)\left(2x+16\right)\cdot\left(7-x\right)=0\)
=>\(-2\left(x-2\right)\cdot2\left(x+8\right)\cdot\left(-1\right)\cdot\left(x-7\right)=0\)
=>\(\left(x-2\right)\left(x+8\right)\left(x-7\right)=0\)
=>\(\left[{}\begin{matrix}x-2=0\\x-7=0\\x+8=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-8\\x=7\end{matrix}\right.\)
Giải:
Có:
\(S=\left(2018-1\right)\left(2018-2\right)...\left(2018-2018\right)+4^3\)
Ta nhân thấy rằng trong tích \(\left(2018-1\right)\left(2018-2\right)...\left(2018-2018\right)\) có một thừa số bằng 0, đó là thừa số \(2018-2018\)
Mà trong một tích, nếu có một thừa số bằng 0 thì tích đó bằng 0
\(\Leftrightarrow\left(2018-1\right)\left(2018-2\right)...\left(2018-2018\right)=0\)
\(\Leftrightarrow S=\left(2018-1\right)\left(2018-2\right)...\left(2018-2018\right)+4^3=0+4^3=4^3=64\)
Vậy \(S=64\)
Chúc bạn học tốt!
S= (2018-1)(2018-2) .... (2018-2017) . 0 +43
=> S= 0 + 43 (Trong 1 tích có 1 thừa số bằng 0 thì tích đó bằng 0);
=>S= 4.4.4=64;
Vậy S=64
\(\frac{-5}{6}\)\(+\)\(\frac{4}{9}\)\(\times\)\(\left(\frac{5}{4}-\frac{2}{3}\right)\)\(\times\)\(\left(-3\right)^2\)\(+\)\(\frac{5}{9}\)\(\times\)\(30\%\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{4}{9}\)\(\times\)\(\frac{7}{12}\)\(\times\)\(9\)\(+\)\(\frac{5}{9}\)\(\times\)\(\frac{3}{10}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{7}{3}\)\(+\)\(\frac{5}{9}\)\(\times\)\(\frac{3}{10}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{7}{3}\)\(+\)\(\frac{1}{6}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{1}{6}\)\(+\)\(\frac{7}{3}\)
\(=\)\(\frac{-2}{3}\)\(+\)\(\frac{7}{3}\)
\(=\)\(\frac{5}{3}\)
Gọi số cần tìm là \(\overline{abcde}\); Số viết thêm là f
\(\Rightarrow\overline{abcdef}=3.\overline{fabcde}\Rightarrow10.\overline{abcde}+f=300000.f+\overline{abcde}\)
\(\Rightarrow7.\overline{abcde}=299999.f\Rightarrow\overline{abcde}=42857\)
\(\Rightarrow f=\left\{1;2\right\}\)
+ Với \(f=1\Rightarrow\overline{abcde}=42857\)
+ Với \(f=2\Rightarrow\overline{abcde}=85714\)
Thử lại chắc chắn đúng. Tự làm nốt nhé
Bài 3:
Gọi số học sinh khối 6 là x
Theo đề, ta có: \(x\in BC\left(12;15;18\right)\)
mà 300<=x<=400
nên x=360
Bài 2:
a: =>3x=27
=>x=9
b: =>2x-3=5
=>2x=8
=>x=4
1: Để C là số nguyên thì 2n+2-3 chia hết cho n+1
=>\(n+1\in\left\{1;-1;3;-3\right\}\)
=>\(n\in\left\{0;-2;2;-4\right\}\)
\(\frac{\frac{3}{11}-\frac{3}{13}+\frac{3}{17}-\frac{3}{19}}{\frac{4}{11}-\frac{4}{13}+\frac{4}{17}-\frac{4}{19}}\)
\(=\frac{3.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{17}-\frac{1}{19}\right)}{4.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{17}-\frac{1}{19}\right)}\)
\(=\frac{3}{4}\)