<span>X+y=4,
4X-5y=7
из первого х=4-у, подставим во второе
4(4-у)-5у=7
16-4у-5у=7
-9у=-9
у=1
х=4-у=3
(3; 1)
</span>
А) 4a(2b+a)
b)9ab(3b2-a2)
вроде так...
Вот тебе решение...........
Ответ:
Переписывать пример не буду, сразу начну решать(1.43):![\frac{(\frac{21}{10}*\frac{1}{2}-1.8)*0.4+0.3 }{0.14}=\frac{(\frac{21}{20}-\frac{18}{10})*0.4+0.3 }{0.14}=\frac{-\frac{15}{20}*0.4-0.3 }{0.14}= \frac{-0.75*0.4-0.3 }{0.14}=\frac{0}{0.14} =0](https://tex.z-dn.net/?f=%5Cfrac%7B%28%5Cfrac%7B21%7D%7B10%7D%2A%5Cfrac%7B1%7D%7B2%7D-1.8%29%2A0.4%2B0.3%20%20%7D%7B0.14%7D%3D%5Cfrac%7B%28%5Cfrac%7B21%7D%7B20%7D-%5Cfrac%7B18%7D%7B10%7D%29%2A0.4%2B0.3%20%20%7D%7B0.14%7D%3D%5Cfrac%7B-%5Cfrac%7B15%7D%7B20%7D%2A0.4-0.3%20%7D%7B0.14%7D%3D%20%20%20%5Cfrac%7B-0.75%2A0.4-0.3%20%7D%7B0.14%7D%3D%5Cfrac%7B0%7D%7B0.14%7D%20%3D0)
![\frac{(\frac{124}{100}-\frac{26}{25})*2.5-\frac{1}{6}*\frac{3}{1} }{12} =\frac{\frac{20}{100}*2.5-\frac{1}{2} }{12}=\frac{0.2*2.5-0.5}{12} = \frac{0}{12} =0](https://tex.z-dn.net/?f=%5Cfrac%7B%28%5Cfrac%7B124%7D%7B100%7D-%5Cfrac%7B26%7D%7B25%7D%29%2A2.5-%5Cfrac%7B1%7D%7B6%7D%2A%5Cfrac%7B3%7D%7B1%7D%20%20%20%20%7D%7B12%7D%20%3D%5Cfrac%7B%5Cfrac%7B20%7D%7B100%7D%2A2.5-%5Cfrac%7B1%7D%7B2%7D%20%20%7D%7B12%7D%3D%5Cfrac%7B0.2%2A2.5-0.5%7D%7B12%7D%20%3D%20%5Cfrac%7B0%7D%7B12%7D%20%3D0)
![\frac{4.34}{10+1.6/(0.6*0.4-0.4)} =\frac{4.34}{10+1.6/(-0.16)} =\frac{4.34}{10-10}=\frac{4.34}{0}](https://tex.z-dn.net/?f=%5Cfrac%7B4.34%7D%7B10%2B1.6%2F%280.6%2A0.4-0.4%29%7D%20%3D%5Cfrac%7B4.34%7D%7B10%2B1.6%2F%28-0.16%29%7D%20%3D%5Cfrac%7B4.34%7D%7B10-10%7D%3D%5Cfrac%7B4.34%7D%7B0%7D)
На ноль делить нельзя, соответственно дробь не имеет смысла.
![\frac{1.1}{\frac{1}{9}+\frac{5}{9}( \frac{4}{30}-\frac{1}{3)} }= \frac{1.1}{\frac{1}{9}+\frac{5}{9}*(-\frac{6}{30}) }=\frac{1.1}{\frac{1}{9}-\frac{2}{18} } =\frac{1.1}{0}](https://tex.z-dn.net/?f=%5Cfrac%7B1.1%7D%7B%5Cfrac%7B1%7D%7B9%7D%2B%5Cfrac%7B5%7D%7B9%7D%28%20%5Cfrac%7B4%7D%7B30%7D-%5Cfrac%7B1%7D%7B3%29%7D%20%20%20%7D%3D%20%5Cfrac%7B1.1%7D%7B%5Cfrac%7B1%7D%7B9%7D%2B%5Cfrac%7B5%7D%7B9%7D%2A%28-%5Cfrac%7B6%7D%7B30%7D%29%20%7D%3D%5Cfrac%7B1.1%7D%7B%5Cfrac%7B1%7D%7B9%7D-%5Cfrac%7B2%7D%7B18%7D%20%20%7D%20%3D%5Cfrac%7B1.1%7D%7B0%7D)
Объяснение: