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5. Scrieți sub forma cea mai simplă inversul numărului raţional)
a=[2-(3 3/4-9/10)×5/19]^2 ÷(1-3/8)
vă rog urgentttt​


Răspuns :

Rezolvare:

[tex]a = \bigg[2- \bigg(3 \dfrac{3}{4} - \dfrac{9}{10} \bigg) \times \dfrac{5}{19} \bigg]^2 : \bigg(1- \dfrac{3}{8}\bigg) \\ [/tex]

[tex]a = \bigg[2- \bigg(\dfrac{12 + 3}{4} - \dfrac{9}{10} \bigg) \times \dfrac{5}{19} \bigg]^2 : \dfrac{8 - 3}{8} \\ [/tex]

[tex]a = \bigg[2- \bigg(\dfrac{^{5)} 15}{4} - \dfrac{^{2)} 9}{10} \bigg) \times \dfrac{5}{19} \bigg]^2 : \dfrac{5}{8} \\ [/tex]

[tex]a = \bigg(2- \dfrac{75 - 18}{20} \times \dfrac{5}{19} \bigg)^2 \times \dfrac{8}{5}[/tex]

[tex]a = \bigg(2- \dfrac{\not 57}{\not20} \times \dfrac{\not5}{\not19} \bigg)^2 \times \dfrac{8}{5}[/tex]

[tex]a = \bigg(^{4)} 2- \dfrac{3}{4}\bigg)^2 \times \dfrac{8}{5}[/tex]

[tex]a = \bigg( \dfrac{8 - 3}{4}\bigg)^2 \times \dfrac{8}{5}[/tex]

[tex]a = \bigg( \dfrac{5}{4}\bigg)^2 \times \dfrac{8}{5}[/tex]

[tex]a = \dfrac{25}{16} \times \dfrac{8}{5}[/tex]

[tex]a = \dfrac{5}{2}[/tex]

Inversul lui a este:

[tex]\boldsymbol {\red{\dfrac{2}{5}}}[/tex]

Efectuăm calculele din parantezele rotunde.

[tex]\it 3\dfrac{3}{4}-\dfrac{9}{10}=\dfrac{^{5)}15}{\ \ 4}-\dfrac{^{2)}9}{\ \ 10}=\dfrac{75-18}{20}=\dfrac{57}{20}\\ \\ \\ 1-\dfrac{3}{8}=\dfrac{5}{8}[/tex]

Acum, expresia devine:

[tex]\it a=\bigg(2-\dfrac{\not57\ ^3}{\not20\ _4}\cdot\dfrac{\not5}{\not19\ _1}\bigg)^2: \dfrac{5}{8}=\bigg(2-\dfrac{3}{4}\bigg)^2\cdot\dfrac{8}{5}=\dfrac{25}{16}\cdot\dfrac{8}{5}=\dfrac{\ 200^{(40}}{80}=\dfrac{5}{2}\\ \\ \\ Inversul\ lui\ \dfrac{5}{2}\ este\ \dfrac{2}{5\ .}[/tex]