Question

Помогите пожалуйста!
2/5x-0,5=21/4
Даю 100 баллов!

Answer 1

$\frac{2}{5} x - 0.5 = \frac{21}{4} \\ 0.4 x- 0.5 = 5.25 \\ 0.4x = 5.25 + 0.5 \\ 0.4x = 5.75 \\ x = 5.75 \div 0.4 \\ x = 14.375$

Answer 2

Ответ:

$1)\ \ \dfrac{2}{5x-0,5}=\dfrac{21}{4}\\\\5x-0,5=\dfrac{2\cdot 4}{21}\ \ ,\ \ \ 5x-0,5=\dfrac{8}{21}\ \ ,\ \ \ 5x=\dfrac{8}{21}+\dfrac{1}{2}\ \ ,\ \ 5x=\dfrac{37}{41}\ ,\\\\x=\dfrac{37}{41\cdot 5}\ \ ,\ \ x=\dfrac{37}{205}\\\\\\2)\ \ \dfrac{2}{5x}-0,5=\dfrac{21}{4}\\\\\dfrac{2}{5x}=\dfrac{21}{4}+\dfrac{1}{2}\ \ ,\ \ \dfrac{2}{5x}=\dfrac{23}{4}\ \ ,\ \ 5x=\dfrac{2\cdot 4}{23}\ \ ,\ \ 5x=\dfrac{8}{23}\ \ ,\ \ x=\dfrac{8}{23\cdot 5}\ ,\\\\x=\dfrac{8}{115}$

$3)\ \ \dfrac{2}{5x}-0,5=2\dfrac{1}{4}\\\\\dfrac{2}{5x}-\dfrac{1}{2}=2\dfrac{1}{4}\ \ ,\ \ \dfrac{2}{5x}=\dfrac{9}{4}+\dfrac{1}{2}\ \ ,\ \ \dfrac{2}{5x}=\dfrac{11}{4}\ \ ,\ \ 5x=\dfrac{2\cdot 4}{11}\ ,\ \ 5x=\dfrac{8}{11}\ ,\\\\x=\dfrac{8}{11\cdot 5}\ \ ,\ \ \ x=\dfrac{8}{55}$