3x⁷ + 5 = 389

3x⁷ = 389 - 5

3x⁷ = 384

x⁷ = 384 : 3

x⁷ = 128

x⁷ = 2⁷

x = 2

\(3.x^7+5=389\)

\(\Rightarrow3.x^7=384\)

\(\Rightarrow x^7=128\)

\(\Rightarrow x^7=2^7\)

\(\Rightarrow x=2\)

Vậy \(x=2\)

b = ( 1+2-3-4) + ( 5+6-7-8) + .............. + (301+302-303-304) + (305 +305)

b = -4 + (-4) + ..................+ (-4) + 610

b= -4 x  76 + 610

b= -304 + 610

b= 306

a.

\(4\times183\times25=4\times25\times183=100\times183=18300\)

b.

\(165\times59+165\times165\times40=165\times\left(59+1+40\right)=165\times100=16500\)

c.

\(56\times49:7=56\times\left(49:7\right)=56\times7=392\)

d.

\(67\times15-57\times15=15\times\left(67-57\right)=15\times10=150\)

\(\left(x-305\right)\times7=26728+19640\\ \left(x-305\right)\times7=46368\\ x-305=46368:7\\ x-305=6624\\ x=6624+305\\ x=6929\)

.

Đáp án B

a) -x-18=12

     -x=12+(-18)

     -x=-6

 =>x=6

-x - 18 = 12

        -x = 12 + 18

        -x = 30

         x = -30

3x - 5 = x + 11

3x - x = 5 + 11

     2x = 16

       x = 8

-39 + x + 165 = -19 + 165

       126 + x = 146

                x = 146 - 126

                x = 20

c)-39+x+165=-19+165

    -39+x+165=146

     -39+x=146-165

     -39+x=-19

            x=-39-(-19)

            x=-20

     k mik nha đang âm điểm

KQ =7

=480:[75+(49-8.3):5]+1

=480:[75+(49-24):5]+1

=480:[75+25:5]+1

=480:[75+5]+1

=480:80+1

=6+1

=7

1: =1/5-1/4=-1/20

2: =6/8-7/8=-1/8

3: =11/18-14/18=-3/18=-1/6

4: =-28/210+90/210+28/210=3/7

5: =-8/17-34/17=-42/17

1)\(\dfrac{1}{5}+\dfrac{-1}{-4}=\dfrac{4}{20}+\dfrac{5}{20}=\dfrac{9}{20}\)

\(\)2)\(\dfrac{3}{4}+\dfrac{-7}{8}=\dfrac{6}{8}+\dfrac{-7}{8}=\dfrac{-1}{8}\)

3)\(\dfrac{11}{18}+\dfrac{-7}{9}=\dfrac{11}{18}+\dfrac{-14}{18}=\dfrac{-3}{18}=\dfrac{-1}{6}\)

4)\(\dfrac{2}{-15}+\dfrac{3}{7}+\dfrac{-4}{-30}=\dfrac{-2}{15}+\dfrac{2}{15}+\dfrac{3}{7}=0+\dfrac{3}{7}=\dfrac{3}{7}\)

5)\(\dfrac{8}{-17}+\left(-2\right)=\dfrac{-8}{17}+\dfrac{-34}{17}=\dfrac{-42}{17}\)