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\(\dfrac{7}{15}+\left(\dfrac{-4}{11}\right)+\dfrac{8}{15}-2,5+\dfrac{7}{15}\)
\(=\dfrac{7}{15}+\left(\dfrac{-4}{11}\right)+\dfrac{8}{15}+\left(\dfrac{-5}{2}\right)+\dfrac{7}{15}\)
\(=\left(\dfrac{7}{15}+\dfrac{8}{15}+\dfrac{7}{15}\right)+\left[\left(\dfrac{-4}{11}\right)+\left(\dfrac{-5}{2}\right)\right]\)
\(=\dfrac{22}{15}+\left(\dfrac{-63}{22}\right)\)
\(=\dfrac{-461}{330}\)
\(=\dfrac{7}{15}+\dfrac{8}{15}+\dfrac{-4}{11}-\dfrac{5}{2}+\dfrac{7}{15}=\dfrac{22}{15}-\dfrac{63}{22}=-\dfrac{461}{330}\)
\(a,\frac{x+8}{3}+\frac{x+7}{2}=-\frac{x}{5}\)
\(\Leftrightarrow\frac{10\cdot\left(x+8\right)}{30}+\frac{15\left(x+7\right)}{30}=\frac{-6x}{30}\)
\(\rightarrow10x+80+15x+105=-6x\)
\(\Leftrightarrow31x+185=0\)
\(\Leftrightarrow x=-\frac{185}{31}\)
b,\(b,\frac{x-8}{3}+\frac{x-7}{4}=4+\frac{1-x}{5}\)
\(\Leftrightarrow\frac{20\left(x-8\right)}{60}+\frac{15\left(x-7\right)}{60}=\frac{240}{60}+\frac{12\left(1-x\right)}{60}\)
\(\rightarrow20x-160+15x-105=240+12-12x\)
\(\Leftrightarrow47x-517=0\)\(\Leftrightarrow x=11\)
Vì 2 phân số bằng nhau nên : 7x-21=5x+25
7x=5x+21+25=5x+46
2x=46( bớt cả hai vế đi 5x)
x=46/2=23
\(Q=\left(\frac{2}{25}-1,008\right):\frac{4}{7}:\left[\left(3\frac{1}{4}-6\frac{5}{9}\right)\cdot2\frac{2}{7}\right]\)
\(Q=\left(\frac{2}{25}-\frac{126}{125}\right):\frac{4}{7}:\frac{-68}{9}\)
\(Q=\frac{-116}{125}:\frac{4}{7}:\frac{-68}{9}\)
\(Q=\frac{-203}{125}:\frac{-68}{9}\)
\(Q=\frac{1827}{8500}\)
\(\frac{8^7.15^7}{4^7.50^7}\)
\(=\left(\frac{8.15}{4.50}\right)^7\)
\(=\left(\frac{2^3.3.5}{2^3.5^2}\right)^7\)
\(=\left(\frac{3}{5}\right)^7\)
\(=\frac{3^7}{5^7}\)
=(2^3)^7.(3.5)^7/(2^2)^7.(2.5^2)^7
=2^21.3^7.5^7/2^14.2^7.5^14
=3^7/5^7
=(3/5)^7