У равнобедренного треугольника боковые стороны равны, значит периметр равен 7+13+13=33 см
1)
1/(√7-√6)-3/(√6-√3)-4/(√7+√3)
![\frac{1}{\sqrt{7}-\sqrt{6}} -\frac{3}{\sqrt{6}-\sqrt{3}} -\frac{4}{\sqrt{7}+\sqrt{3}} = \frac{1*(\sqrt{7}+\sqrt{6})}{(\sqrt{7}-\sqrt{6})(\sqrt{7}+\sqrt{6})} -\frac{3*(\sqrt{6}+\sqrt{3})}{(\sqrt{6}-\sqrt{3})*(\sqrt{6}+\sqrt{3})} -\frac{4*(\sqrt{7}-\sqrt{3})}{(\sqrt{7}+\sqrt{3})*((\sqrt{7}-\sqrt{3}))} = \frac{(\sqrt{7}+\sqrt{6})}{1} -\frac{3*(\sqrt{6}+\sqrt{3})}{6-3} -\frac{4*(\sqrt{7}-\sqrt{3})}{7-3} =](https://tex.z-dn.net/?f=+%5Cfrac%7B1%7D%7B%5Csqrt%7B7%7D-%5Csqrt%7B6%7D%7D++-%5Cfrac%7B3%7D%7B%5Csqrt%7B6%7D-%5Csqrt%7B3%7D%7D+-%5Cfrac%7B4%7D%7B%5Csqrt%7B7%7D%2B%5Csqrt%7B3%7D%7D++%3D+%5Cfrac%7B1%2A%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%7D%7B%28%5Csqrt%7B7%7D-%5Csqrt%7B6%7D%29%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%7D++-%5Cfrac%7B3%2A%28%5Csqrt%7B6%7D%2B%5Csqrt%7B3%7D%29%7D%7B%28%5Csqrt%7B6%7D-%5Csqrt%7B3%7D%29%2A%28%5Csqrt%7B6%7D%2B%5Csqrt%7B3%7D%29%7D+-%5Cfrac%7B4%2A%28%5Csqrt%7B7%7D-%5Csqrt%7B3%7D%29%7D%7B%28%5Csqrt%7B7%7D%2B%5Csqrt%7B3%7D%29%2A%28%28%5Csqrt%7B7%7D-%5Csqrt%7B3%7D%29%29%7D++%3D+%5Cfrac%7B%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%7D%7B1%7D+-%5Cfrac%7B3%2A%28%5Csqrt%7B6%7D%2B%5Csqrt%7B3%7D%29%7D%7B6-3%7D+-%5Cfrac%7B4%2A%28%5Csqrt%7B7%7D-%5Csqrt%7B3%7D%29%7D%7B7-3%7D+%3D++++)
![\frac{(\sqrt{7}+\sqrt{6})}{1} -\frac{3*(\sqrt{6}+\sqrt{3})}{3} -\frac{4*(\sqrt{7}-\sqrt{3})}{4} = \sqrt{7} +\sqrt{6} -\sqrt{6} -\sqrt{3} -\sqrt{7} +\sqrt{3} =0](https://tex.z-dn.net/?f=+%5Cfrac%7B%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%7D%7B1%7D+-%5Cfrac%7B3%2A%28%5Csqrt%7B6%7D%2B%5Csqrt%7B3%7D%29%7D%7B3%7D+-%5Cfrac%7B4%2A%28%5Csqrt%7B7%7D-%5Csqrt%7B3%7D%29%7D%7B4%7D+%3D+%5Csqrt%7B7%7D+%2B%5Csqrt%7B6%7D+-%5Csqrt%7B6%7D+-%5Csqrt%7B3%7D+-%5Csqrt%7B7%7D+%2B%5Csqrt%7B3%7D+%3D0+)
2) 2a²-5ab+2b²
при a=√7+√6 и b=√7-√6;
![2*(\sqrt{7}+\sqrt{6})^2 -5*(\sqrt{7}+\sqrt{6})(\sqrt{7}-\sqrt{6})+2*(\sqrt{7}-\sqrt{6})^2=2*(7+2\sqrt{7*6}+6) -5*(7-6)+2*(7-2\sqrt{7*6}+6)=2*(13+2\sqrt{42} )-5+2*2*(13+2\sqrt{42} )=26+4\sqrt{42} -5+26+4\sqrt{42} =52](https://tex.z-dn.net/?f=+2%2A%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%5E2++-5%2A%28%5Csqrt%7B7%7D%2B%5Csqrt%7B6%7D%29%28%5Csqrt%7B7%7D-%5Csqrt%7B6%7D%29%2B2%2A%28%5Csqrt%7B7%7D-%5Csqrt%7B6%7D%29%5E2%3D2%2A%287%2B2%5Csqrt%7B7%2A6%7D%2B6%29+-5%2A%287-6%29%2B2%2A%287-2%5Csqrt%7B7%2A6%7D%2B6%29%3D2%2A%2813%2B2%5Csqrt%7B42%7D+%29-5%2B2%2A2%2A%2813%2B2%5Csqrt%7B42%7D+%29%3D26%2B4%5Csqrt%7B42%7D+-5%2B26%2B4%5Csqrt%7B42%7D+%3D52+)
3) ![3\sqrt{3*\frac{2}{3}} -\sqrt{132} +4*\sqrt{2*\frac{1}{16}} = 3\sqrt{2} -\sqrt{4*33} +4*\frac{1}{4}\sqrt{2} = 3\sqrt{2} -2\sqrt{33} +\sqrt{2} = 4\sqrt{2} -2\sqrt{33} = 2(2\sqrt{2} -\sqrt{33})](https://tex.z-dn.net/?f=+3%5Csqrt%7B3%2A%5Cfrac%7B2%7D%7B3%7D%7D+-%5Csqrt%7B132%7D++%2B4%2A%5Csqrt%7B2%2A%5Cfrac%7B1%7D%7B16%7D%7D+%3D+3%5Csqrt%7B2%7D+-%5Csqrt%7B4%2A33%7D++%2B4%2A%5Cfrac%7B1%7D%7B4%7D%5Csqrt%7B2%7D+%3D+++3%5Csqrt%7B2%7D+-2%5Csqrt%7B33%7D++%2B%5Csqrt%7B2%7D+%3D+4%5Csqrt%7B2%7D+-2%5Csqrt%7B33%7D+%3D++++2%282%5Csqrt%7B2%7D+-%5Csqrt%7B33%7D%29++++)
475+425=900 кирпичей всего
3600:900=4 кг весит 1 кирпич
475*4=1900 кг масса кр. кирп.
425*4=1700 кг масса бел. кирп.
1900+1700=3600 кг масса всех кирп.
3600:900=4 кг 1 кирп.
1900:4=475 штук крас.
1700:4=425 штук бел.
Пишем, как сказано:
П=0.35В, Т=0.8В, 0.8В- 0.35В= 18, 0.45В=18, В=40, Первое=40*0.35= 14 -ответ
Ответ: искомая вероятность 2/(9+5+2)=2/16=1/8.
Пошаговое объяснение: