Ta có:

\(12:\left\{390:\left[500-\left(5^3+7^2.5\right)\right]\right\}\)

\(=12:\left\{390:\left[500-125-245\right]\right\}\)

\(=12:\left(390:130\right)\)

\(=12:3=4\)

=4                         

a) x(x+1)=2+4+6+8+...+2500

x(x+1)=(2500+2).1250:2

x(x+1)=1563750

Ta thấy: x và x+1 là 2 số liên tiếp

Mà x(x+1)=1563750=>x=1250;x+1=1251

Vậy x=1250

b) x-3=12:{390:[500-(5^3+7^2.5)]}

x-3=12:[390:(500-254.64)]

x-3=12:(390:245.35)

x-3=12:1.58

x-3=7.54

=>x=10.5

Vậy x=10.5

c) x+3^3.12=3^3.19

=>x=2.46

Vậy x=2.46

\(=\)\(\frac{2^{12}.5^7+2^{12}.5^6}{2^{15}.5^6+2^{12}.5^6}\)

\(=\)\(\frac{2^{12}.5^6.\left(1+5\right)}{2^{12}.5^6.\left(2^3+1\right)}\)

\(=\)\(\frac{6}{9}\)\(=\)\(\frac{2}{3}\)

chúc học tốt

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

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

0,5555897934

\(\frac{2^{12}\cdot5^7+4^6\cdot25^3}{8^5\cdot25^3+\left(2^2\cdot5\right)^6}\)

\(=\frac{2^{12}.5^7+2^{12}\cdot5^6}{2^{15}\cdot5^6+2^{12}\cdot5^6}\)

\(=\frac{2^{12}\cdot5^6\cdot\left(1\cdot5+1\right)}{2^{12}\cdot5^6\cdot\left(2^3\cdot1+1\right)}\)

\(=\frac{6}{9}\)

\(=\frac{2}{3}\)

\(\frac{2^{12}.5^7+4^6.25^3}{8^5.25^3+\left(2^2.5\right)^6}=\frac{2^{12}.5^7+\left(2^2\right)^6.\left(5^2\right)^3}{\left(2^3\right)^5.\left(5^2\right)^3+\left(2^2\right)^6.5^6}=\frac{2^{12}.5^7+2^{12}.5^6}{2^{15}.5^6+2^{12}.5^6}\)

                                 \(=\frac{2^{12}.5^6.\left(5+1\right)}{2^{12}.5^6.\left(2^3+1\right)}=\frac{6}{9}=\frac{2}{3}\)

(7x -12)^5=9.5-13

(7x-12)^5=45-13

(7x-12)^5=32

(7x-12)^5=2^5

7x-12=2

7x=2+12

7x=14

x=14:7

x=2

tick