x+9-2).(-3)=/-7/

x+6=7

x=7-6

x=1

Vậy x=1

\(x+\left(-2\right).\left(-3\right)=\left|-7\right|\)

\(\Rightarrow x+\left(-2\right).\left(-3\right)=7\)

\(\Rightarrow x+6=7\)

\(\Rightarrow x=7-6\)

\(\Rightarrow x=1\)

umk mk theo dõi bn rùi

ukm

Ta có: \(\frac{1}{21}>\frac{1}{30};\frac{1}{22}>\frac{1}{30};\ldots;\frac{1}{30}=\frac{1}{30}\)

Do đó: \(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}>\frac{1}{30}+\frac{1}{30}+\cdots+\frac{1}{30}=\frac{10}{30}=\frac13\) (1)

Ta có: \(\frac{1}{31}>\frac{1}{40};\frac{1}{32}>\frac{1}{40};\ldots;\frac{1}{40}=\frac{1}{40}\)

Do đó: \(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}>\frac{1}{40}+\frac{1}{40}+\cdots+\frac{1}{40}=\frac{10}{40}=\frac14\) (2)

Ta có: \(\frac{1}{41}>\frac{1}{50};\frac{1}{42}>\frac{1}{50};\ldots;\frac{1}{50}=\frac{1}{50}\)

Do đó: \(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}>\frac{1}{50}+\frac{1}{50}+\cdots+\frac{1}{50}=\frac{10}{50}=\frac15\) (3)

Từ (1),(2),(3) suy ra \(\left(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}\right)+\left(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}\right)+\left(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}\right)>\frac13+\frac14+\frac15=\frac{47}{60}\)

c: \(\Leftrightarrow4^x\cdot15=60\)

hay x=1

ta có:

125⁷⁹=(5³)⁷⁹

625⁶⁰=(5⁴)⁶⁰

=>5³<5⁴ =>(5³)⁷⁹<(5⁴)⁶⁰

=>125⁷⁹<625⁶⁰

lâu rồi ko lm ko bt đúng ko

Ta có: \(125^{79}=\left(5^3\right)^{79}=5^{237}\)

\(625^{60}=\left(5^4\right)^{60}=5^{240}\)

Vì \(5^{237}< 5^{240}\)nên \(125^{79}< 625^{60}\)

96 - 3 ( x + 1 ) = 42

=>3(x+1)=54

=>x+1=18

=>x=17

80 - { 130 - (12 -4 )}

=80-{130-8}

=80-122

=-42

a) 0,75 : 4,5 = \(\frac{1}{15}\) : 2x

=> \(\frac{0,75}{4,5}\) = \(\frac{\frac{1}{15}}{2x}\)

=> 0,75 . 2x = \(\frac{1}{15}\) . 4,5

=> 0,75 . 2x = 0,3

=> 2x            = 0,3 : 0,75

=> 2x            = 0,4

=> x               = 0,4 : 2

=>x                = 0,2