Т.к 1/5 поля=42га,то 4*42=168га
Т.е. 168 га занято картофелем
<span>(7a -1)(a+5)=(3+7a)(a+3)
7а</span>²-а+35а-5=3а+7а²+9+21а
7а²-а+35а-3а-7а²-21a=9+5
10a=14
а=14:10
а=1,4
<span>Подставь вместо у=0,15 и посчитай</span>
Ответ:
Пошаговое объяснение:
a) z1+z2=7-2i+(-2+3i)=7-2+3i-2i=5+i
z1-z2=7-2i-(-2+3i)=7+2-2i-3i=9-5i
z1*z2=(7-2i)(-2+3i)=-14+21i+4i-6![i^{2}[/tex=-14+25i+6=-8+25i</p><p> z1/z2=[tex]\frac{7-2i}{-2+3i} =\frac{(7-2i)(2+3i)}{(-2+3i)(2+3i)} =\frac{14-4i+21i-6i^{2} }{-4+9i^{2} } =\frac{20+17i}{-4-9} =-\frac{20+17i}{13}](https://tex.z-dn.net/?f=i%5E%7B2%7D%5B%2Ftex%3D-14%2B25i%2B6%3D-8%2B25i%3C%2Fp%3E%3Cp%3E%20%20%20z1%2Fz2%3D%5Btex%5D%5Cfrac%7B7-2i%7D%7B-2%2B3i%7D%20%3D%5Cfrac%7B%287-2i%29%282%2B3i%29%7D%7B%28-2%2B3i%29%282%2B3i%29%7D%20%3D%5Cfrac%7B14-4i%2B21i-6i%5E%7B2%7D%20%7D%7B-4%2B9i%5E%7B2%7D%20%7D%20%3D%5Cfrac%7B20%2B17i%7D%7B-4-9%7D%20%3D-%5Cfrac%7B20%2B17i%7D%7B13%7D)
б) z1=-2-4i; z2=5-3i
z1+z2=-2-4i+5-3i=3-7i
z1-z2=-2-4i-(5-3i)=-2-4i-5+3i=-7-i
z1*z2=(-2-4i)*(5-3i)=-10+6i-20i+12
=-22-14i
![\frac{z1}{z2} =\frac{-2-4i}{5-3i} =\frac{(-2-4i)(5+3i)}{(5-3i)(5+3i)} =\frac{-10-6i-20i-12i^{2} }{25-9i^{2} } =\frac{2-26i}{34}](https://tex.z-dn.net/?f=%5Cfrac%7Bz1%7D%7Bz2%7D%20%3D%5Cfrac%7B-2-4i%7D%7B5-3i%7D%20%3D%5Cfrac%7B%28-2-4i%29%285%2B3i%29%7D%7B%285-3i%29%285%2B3i%29%7D%20%3D%5Cfrac%7B-10-6i-20i-12i%5E%7B2%7D%20%7D%7B25-9i%5E%7B2%7D%20%7D%20%3D%5Cfrac%7B2-26i%7D%7B34%7D)