12.3 x 4,5 + 4,5 x 7,7

=4,5 x (12,3 + 7,7 )

=4,5 x 20

=90

12,3 x 4,5 + 4,5 x 77

= (12,3 + 77) x 4,5

= 20 x 4,5 

= 90

:))

x=4,5...

ra hình trái tym :)

Đáp án D

\(80-\left(4.5^2-3.2^3\right)=2^{10}-\left(x-4\right)\\ 80-\left(4.25-3.8\right)=1024-\left(x-4\right)\\ 80-\left(100-24\right)=1024-\left(x-4\right)\\ 80-76=1024-\left(x-4\right)\\ 4=1024-\left(x-4\right)\\ x-4=1024-4\\ x-4=1024-4\\ x-4=1020\\ x=1020+4\\ x=1024\)

80-(4.5²-3.2³)=2¹⁰-(x-4)

80-(4.25-3.8)=1024-(x-4)

80-(100-24)=1024-(x-4)

         80-76=1024-(x-4)

                4=1024-(x-4)

      4-1024= x-4

          1020= x-4

      1020+4=x

          1024=x

a/|x|-2,5=27,5

=>|x|=27,5+2,5=30

=>x=30 hoặc x=-30

b/\(\dfrac{3}{4}+\dfrac{2}{5}.x=\dfrac{29}{60}\)

=>\(\dfrac{2}{5}.x\)=\(\dfrac{29}{60}-\dfrac{3}{4}\)=\(\dfrac{-4}{15}\)

=>x=\(\dfrac{-4}{15}:\dfrac{2}{5}\)=\(\dfrac{-2}{3}\)

c/(x-1)\(^5\)=-32

=>x-1=-2 vì (-2)\(^5\)=-32

=>x=-2+1=-1

d/\(\dfrac{4}{5}.x+0,5=4.5\)

=>\(\dfrac{4}{5}.x+0,5=20\)

=>\(\dfrac{4}{5}.x=20-0,5=19,5\)

=>\(x=19,5:\dfrac{4}{5}\)=\(\dfrac{195}{8}\)

\(\left(4^3-11x\right).5^3=4.5^4\)

\(\Rightarrow\left(4^3-11x\right)=4.5^4\div5^3\)

\(\Rightarrow4^3-11x=20\)

\(\Rightarrow11x=4^3-20\)

\(\Rightarrow11x=44\)

\(\Rightarrow x=4\)

(4³ - 11 . x) . 5³ = 4 . 5⁴ = 2500

(4³ - 11 . x)        = 2500 : 125

4³ - 11 . x            = 20

11 . x                   = 4³ - 20

11 . x                   = 44

x                         = 44 : 11

x                          = 4

Học tốt!!!