54,47 x 8 + 54,47 x 4 - 54,47 : 0 ,5

= 54,47 x 8 + 54,47 x 4 - 54,47 x 2

= 54,47 x (8 + 4 - 2)

= 54,47 x (12 - 2)

= 54,47 x 10

= 544,7

=54,47 x 8 + 54,47 x 4 - 54,47 x 2

=54,47 x (8+4-2)

=54,47 x 10 = 544,7

\(-7\left(3x-5\right)+2\left(7x-14\right)=28\)

\(-21x+35+14x-28=28\)

\(-7x+7=28\)

\(-7x=28-7\)

\(-7x=21\)

\(x=21:\left(-7\right)\)

\(x=-3\)

-7(3\(x\) - 5) + 2.(7\(x\) - 14) = 28

-21\(x\) + 35 + 14\(x\) - 28 = 28

(-21\(x\) + 14\(x\)) = 28 +28 - 35

- 7\(x\) = 56 - 35

- 7\(x=21\)

\(x=21:\left(-7\right)\)

\(x=-3\)

Vậy \(x=-3\)

a ) Ta có : 4(x - 5) - 3(x + 7) = -19 <=> 4x - 20 - 3x - 21 = -19 => x - 41 = -19 => x = -19 + 41 => x = 22 b) Ta có " 7(x - 3) - 5(3 - x) = 11x - 5 <=> 7x - 21 - 15 + 5x = 11x - 5 <=> 12x - 36 = 11x - 5 => 12x - 11x = -5 + 36 => x = 31

Ko bao giờ

Ko bao giờ 

10

4,7

4,7

5,95

1\(\) 1254

\(1\dfrac{13}{15}\cdot0,75-\left(\dfrac{11}{20}+25\%\right)\cdot\dfrac{7}{5}\)

\(=\dfrac{28}{15}\cdot\dfrac{3}{4}-\left(0,55+0,25\right)\cdot\dfrac{7}{5}\)

\(=\dfrac{7}{5}-0,8\cdot\dfrac{7}{5}=\dfrac{7}{5}\cdot0,2=\dfrac{7}{5}\cdot\dfrac{1}{5}=\dfrac{7}{25}\)

c) Các tỉ lệ thức có thể lập:

\(\dfrac{-2}{-9}=\dfrac{-6}{-27}\)

\(\dfrac{-2}{-6}=\dfrac{-9}{-27}\)

\(\dfrac{-9}{-2}=\dfrac{-27}{-6}\)

\(\dfrac{-6}{-2}=\dfrac{-27}{-9}\)

a) Các tỉ lệ thức có thể lập:

\(\dfrac{7}{-49}=\dfrac{4}{-28}\)

\(\dfrac{7}{4}=\dfrac{-49}{-28}\)

\(\dfrac{-49}{7}=\dfrac{-28}{4}\)

\(\dfrac{4}{7}=\dfrac{-28}{-49}\)

\(x^2+2=6\)

\(x^2=6-2\)

\(x^2=4\)

\(x=-2\) hoặc \(x=2\)

Vậy \(S=\left\{-2;2\right\}\)

\(x^2\) + 2 = 6

\(x^2\) = 6 - 2

\(x^2\) = 4

Vì \(x^2\) = 4 nên x = 2 hoặc -2

Vậy x={2;-2}.