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{x2 - [62 - (64 -9 .7)3 -7.5]3 - 5.3}3=1
{x2 - [62 - (64 - 63)3 -7.5]3 - 5.3}3=1
{x2 - [62 - 13 -7.5]3 - 5.3}3=1
{x2 - [36 - 1 -7.5]3 - 5.3}3=1
{x2 - [36 - 1 - 35]3 - 5.3}3=1
{x2 - [35 - 35]3 - 5.3}3=1
{x2 - 03 - 5.3}3=1
{x2 - 0 -5.3}3=1
{x2 - 0 - 15}3=1
{x.x - 0 - 15}3=1
{x.x + 0+15}3=1
{x.x +15}3=1
nếu x bằng 1 thì:(1.1+15)3 không bằng 1
---------------2 thì:(2.2+15)3 ------------------1
-------------- 3 thì:(3.3+15)3-------------------1
-------------- 4 thì:(4.4+15)3 bằng 1
Vậy x bằng 4
{ x2 - [ 62 - ( 82 - 9.7)3 - 7.5]3 - 5.3 }3 = 1
{ x2 + [ 36 - (64 - 63)3 - 35]3 - 15}3 = 1
[ x2 - ( 36 - 13 - 35 ) - 15 ]3 = 1
[ x2 - ( 36 - 1 - 35 ) - 15]3 = 1
[ x2 - ( 35 - 35 ) - 15]3 = 1
[ x2 - 0 - 15]3 = 1
( x2 - 15 )3 = 1
<=> ( x2 - 15)3 = 13
=> x2 - 15 = 1
<=> x2 = 16
=> x = 4
\(\frac{3^{10}+6^2}{5\cdot3^8+20}\)
\(=\frac{3^{10}+\left(3 \cdot2\right)^2}{5\cdot3^8+5\cdot4}\)
\(=\frac{3^{10}+3^2\cdot2^2}{5\cdot\left(3^8+4\right)}\)
\(=\frac{3^2\cdot\left(3^8+2^2\right)}{5\cdot\left(3^8+4\right)}\)
\(=\frac{3^2\cdot\left(3^8+4\right)}{5\cdot\left(3^8+4\right)}\)
\(=\frac{3^2}{5}\)
\(=\frac{9}{5}\)
(-12.\(\dfrac{2}{7}\) + \(\dfrac{8}{9}\): 3\(\dfrac{1}{2}\) - \(\dfrac{2}{7}\).\(\dfrac{5}{18}\)). 3\(\dfrac{1}{2}\)
(-\(\dfrac{24}{7}\) + \(\dfrac{8}{9}\):\(\dfrac{7}{2}\) - \(\dfrac{5}{63}\)). \(\dfrac{7}{2}\)
= (-\(\dfrac{24}{7}\) + \(\dfrac{16}{63}\) - \(\dfrac{5}{63}\)).\(\dfrac{7}{2}\)
= (\(-\dfrac{216}{63}\) + \(\dfrac{16}{63}\) - \(\dfrac{5}{63}\)). \(\dfrac{7}{2}\)
= - \(\dfrac{205}{63}\). \(\dfrac{7}{2}\)
= - \(\dfrac{205}{18}\)
2a) \(\frac{3^6+45^4-15^3.4^5}{27^4.25^3+45^6}\)
= \(\frac{3^6+\left(3^2.5\right)^4-\left(3.5\right)^3.\left(2^2\right)^5}{\left(3^3\right)^4.\left(5^2\right)^3+\left(3^2.5\right)^6}\)
= \(\frac{3^6+3^8.5^4-3^3.5^3.4^{10}}{3^{12}.5^6-3^{12}.5^6}=\frac{3^3.\left(3^3+3^5.5^4-5^3.4^{10}\right)}{0}\)(xem lại đề)
b) \(\frac{\left(\frac{2}{5}\right)^7.5^7+\left(\frac{16}{3}\right)^3:\left(\frac{4}{9}\right)^3}{2^7.5^2+512}\)
= \(\frac{\left(\frac{2}{5}.5\right)^7+\left(\frac{16}{3}:\frac{4}{9}\right)^3}{2^7.5^2+2^9}\)
= \(\frac{2^7+12^3}{2^7\left(5^2+2^2\right)}\)
= \(\frac{2^7+\left(2^2.3\right)^3}{2^7.29}\)
= \(\frac{2^7+2^6.3^3}{2^7.29}\)
= \(\frac{2^6\left(1+27\right)}{2^7.29}=\frac{28}{2.29}=\frac{14}{29}\)
1: \(5\cdot3^x=5\cdot3^4\)
nên \(3^x=3^4\)
hay x=4
2: \(7\cdot4^x=7\cdot4^3\)
nên \(4^x=4^3\)
hay x=3
3: \(8\cdot7^x=8\cdot7^6\)
nên \(7^x=7^6\)
hay x=6