A=5*7
а=35
б=48/8
б=6
с=54/9
с=6
д=42/6
д=7
Как не любят люди скобок...
![\it \displaystyle \int\limits^5_1 \frac{dx}{x+\sqrt{2x-1}}= \int\limits^3_1\frac{tdt}{\frac{t^2+1}{2}+t}=2\int\limits^3_1\frac{tdt}{(t+1)^2}=\\=2\int\limits^3_1(\frac{1}{t+1}-\frac{1}{(t+1)^2})dt=(2ln|t+1|+\frac{2}{t+1})|^3_1=\\=2ln|4|-2ln|2|+\frac{1}{2}-1=2ln|2|-0,5\approx0,87\\\\\\\\2x-1=t^2\\x=\frac{t^2+1}{2}\\dx=tdt\\t_1=\sqrt{2*5-1}=3\\t_2=\sqrt{2-1}=1\\\\\\\\\frac{t}{(t+1)^2}=\frac{A}{t+1}+\frac{B}{(t+1)^2}\\t=A(t+1)+B\\t|1=A\\t^0|0=A+B=\ \textgreater \ B=-1](https://tex.z-dn.net/?f=+%5Cit+%5Cdisplaystyle+%5Cint%5Climits%5E5_1+%5Cfrac%7Bdx%7D%7Bx%2B%5Csqrt%7B2x-1%7D%7D%3D+%5Cint%5Climits%5E3_1%5Cfrac%7Btdt%7D%7B%5Cfrac%7Bt%5E2%2B1%7D%7B2%7D%2Bt%7D%3D2%5Cint%5Climits%5E3_1%5Cfrac%7Btdt%7D%7B%28t%2B1%29%5E2%7D%3D%5C%5C%3D2%5Cint%5Climits%5E3_1%28%5Cfrac%7B1%7D%7Bt%2B1%7D-%5Cfrac%7B1%7D%7B%28t%2B1%29%5E2%7D%29dt%3D%282ln%7Ct%2B1%7C%2B%5Cfrac%7B2%7D%7Bt%2B1%7D%29%7C%5E3_1%3D%5C%5C%3D2ln%7C4%7C-2ln%7C2%7C%2B%5Cfrac%7B1%7D%7B2%7D-1%3D2ln%7C2%7C-0%2C5%5Capprox0%2C87%5C%5C%5C%5C%5C%5C%5C%5C2x-1%3Dt%5E2%5C%5Cx%3D%5Cfrac%7Bt%5E2%2B1%7D%7B2%7D%5C%5Cdx%3Dtdt%5C%5Ct_1%3D%5Csqrt%7B2%2A5-1%7D%3D3%5C%5Ct_2%3D%5Csqrt%7B2-1%7D%3D1%5C%5C%5C%5C%5C%5C%5C%5C%5Cfrac%7Bt%7D%7B%28t%2B1%29%5E2%7D%3D%5Cfrac%7BA%7D%7Bt%2B1%7D%2B%5Cfrac%7BB%7D%7B%28t%2B1%29%5E2%7D%5C%5Ct%3DA%28t%2B1%29%2BB%5C%5Ct%7C1%3DA%5C%5Ct%5E0%7C0%3DA%2BB%3D%5C+%5Ctextgreater+%5C+B%3D-1)
В кубе 12 ребер.
а) 168:12=14см - длина одного ребра. Площадь грани равна 14*14=196см². В кубе 6 граней. S=6*196=1176см².
б) 19,2:12=1,6. S=1,6*1,6*6=15,36 ед²
в) 252см:12=21см. S=21*21*6=2646см³=0,2646м²
1.а)128+(а+472), если а=147
128+(а+472)= 128+(147+472)=128+619=747
б)(б+168)-78, если б=210
(б+168)-78=(210+168)-78=378-78=300
2. а)568-х=436
х=568-436
х=132