\(76-\left\{2\cdot\left[2\cdot5^2-\left(31-2\cdot3\right)\right]\right\}\)

\(=76-\left\{2\cdot\left[2\cdot25-\left(31-6\right)\right]\right\}\)

\(=75-\left[2\cdot\left(50-25\right)\right]\)

\(=76-\left(2\cdot25\right)\)

\(=76-50\)

\(=26\)

____________________

\(6^2\cdot10:\left\{780:\left[10^3-\left(2\cdot5^3+35\cdot14\right)\right]\right\}\)

\(=36\cdot10:\left\{780:\left[1000-\left(2\cdot125+490\right)\right]\right\}\)

\(=360:\left\{780:\left[1000-\left(250+490\right)\right]\right\}\)

\(=360:\left[780:\left(1000-740\right)\right]\)

\(=360:\left(780:260\right)\)

\(=360:3\)

\(=120\)

a: =76-{2*[2*25-31+6]}

=76-{2*[50-31+6]}

=76-2*25

=76-50=26

b: \(=360:\left\{\dfrac{780}{1000-2\cdot125-490}\right\}\)

\(=360:\dfrac{780}{260}\)

=360/3=120

1) \(7.4^x=7.4^3\Leftrightarrow4^x=4^3;x=3\)

2) \(\frac{3}{2.5^x}=\frac{3}{2.5^{12}}\Leftrightarrow5^x=5^{12};x=12\)

\(2^x=2.2^8=2^9;x=9\)

4) \(5.3^x=7.3^5-2.3^5\Leftrightarrow5.3^x=3^5.\left(7-2\right)\)

\(\Leftrightarrow3^5.x=3^5.5;x=5\)

tính nhanh à       

mình không hiểu

c) \(3^2+2^4-\left(6^8:6^6-6^2\right)< 5^x< 125\)

\(=9+16-\left(6^{8-6}-36\right)< 5^x< 5^3\)

\(=25-\left(6^2-36\right)< 5^x< 5^3\)

\(=25-\left(36-36\right)< 5^x< 5^3\)

\(=25-0< 5^x< 5^3\)

\(=25< 5^x< 5^3\)

\(=5^2< 5^x< 5^3\)

Vì \(5^2=25\) và \(5^3=125\) nên \(x\) không thể thỏa mãn đề bài

⇒ \(x\) không thỏa mãn đề bài

là bằng 120 

thank you 

BCNN=120

1062882

\(\frac{2^3.3}{2^2.3^2.5}=\frac{2}{3.5}=\frac{2}{15}\)

\(2^3.\frac{3}{2^2}.3^2.5=8.\frac{3}{4}.9.5=6.9.5=54.5=270\)

76 - { 2 . [ 2 . 5² - ( 31 - 2.3 ) ] } + 3. 25

= 76 - { 2 .[  50 - ( 31 - 6 ) ] } + 75

= 76 - {2 . [ 50 - 25 ]  } + 75

= 76 - { 2 . 25 } + 75

= 76 - 100 + 75

= 51.

\(5^{2x-3}-2\cdot5^2=5^2\cdot3\)

\(\Rightarrow5^{2x-3}-50=75\)

\(\Rightarrow5^{2x-3}=75+50\)

\(\Rightarrow5^{2x-3}=125\)

\(\Rightarrow5^{2x-3}=5^3\)

\(\Rightarrow2x-3=3\)

\(\Rightarrow2x=6\)

\(\Rightarrow x=\dfrac{6}{2}=3\)