\(2n+6+\frac{9}{3}+\left(\frac{50}{6}\text{ : }3\right)=100\)
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a)
\(\frac{0,24x450+0.8x15x3+3x3x8}{65-60+55-50+...+25-2+5}\)
\(=\frac{0,24x45x10+0,8x45+3x3x8}{\left(65-60\right)+\left(55-50\right)+...+\left(25-20\right)+5}\)
\(=\frac{45\left(0,24x10+0,8\right)+3x3x8}{5+5+...+5}\)
\(=\frac{45x2,4+45x0,8+3x3x4x2}{5x6}\)
\(=\frac{108+36+36x2}{5x6}=\frac{36x3+36+36x2}{5x6}\)
\(=\frac{36\left(3+1+2\right)}{5x6}=\frac{36x6}{5x6}=\frac{36}{5}\)
b)
\(\frac{\left(23,4+19,5\right)\times7+\left(23,4+19,5\right)\times3+11}{0,55\times2\times30+5\times11+2,75\times8}\)
\(=\frac{\left(23,4+19,5\right)\times\left(7+3\right)+11}{1,1\times30+5\times11+2\times11}\)
\(=\frac{42,9\times10+11}{33+11\left(5+2\right)}=\frac{440}{33+77}=\frac{440}{110}=4\)
Cách này không hay lắm. Mong bạn thông cảm!
\(\left(\frac{3}{7}\right)^{21}:\left(\frac{9}{49}\right)^6\)\(=\left(\frac{3}{7}\right)^{21}:\left(\frac{3}{7}\right)^{2^6}\)\(=\left(\frac{3}{7}\right)^{21}:\left(\frac{3}{7}\right)^{12}\)
\(=\left(\frac{3}{7}\right)^{21-12}\)\(=\left(\frac{3}{7}\right)^9\)
\(\left(\frac{3}{7}\right)^{21}:\left(\frac{9}{49}\right)^6\)
\(=\left(\frac{3}{7}\right)^9.\left(\frac{3}{7}\right)^{12}:\left[\left(\frac{3}{7}\right)^2\right]^6\)
\(=\left(\frac{3}{7}\right)^9.\left(\frac{3}{7}\right)^{12}:\left(\frac{3}{7}\right)^{12}\)
\(=\left(\frac{3}{7}\right)^9=\frac{3^9}{7^9}=\frac{19683}{40353607}\)
áp dụng t/c dãy tỉ số bằng nhau ta có:
1+3y/12=1+7y/4x=2+10y/12+4x=2(1+5y)/2(6+2x)
=1+5y/6+2x
do đó : 1+5y/6+2x=1+5y/5x<=>6+2x=5x<=>6=5x-2x
<=>3x=6=>x=2
Vậy x=2. chúc bạn học tốt
\(2n+6+\frac{9}{3}+\left(\frac{50}{6}\text{ : }3\right)=100\)
\(2n+6+3+\left(\frac{25}{3}\cdot\frac{1}{3}\right)=100\)
\(2n+9+\frac{25}{9}=100\)
\(2n+\frac{81}{9}+\frac{25}{9}=100\)
\(2n+\frac{106}{9}=100\)
\(2n=100-\frac{106}{9}\)
\(2n=\frac{794}{9}\)
\(n=\frac{794}{9}\text{ : }2\)
\(n=\frac{794}{9}\cdot\frac{1}{2}\)
\(n=\frac{397}{2}\)
Nhầm !
\(n=\frac{397}{9}\)
Hihi ! ^_^
Sorry !