<span>3x²+16x-12=0</span>
D=256+144=400=20²
<span>x1=(-16-20)/6=-6
x2=(-16+20)/6=2/3</span>
![(\sqrt7-3,5)(12-3x)\ \textgreater \ 0\\12-3x\ \textless \ 0\\3x\ \textgreater \ 12\\x\ \textgreater \ 4](https://tex.z-dn.net/?f=+%28%5Csqrt7-3%2C5%29%2812-3x%29%5C+%5Ctextgreater+%5C+0%5C%5C12-3x%5C+%5Ctextless+%5C+0%5C%5C3x%5C+%5Ctextgreater+%5C+12%5C%5Cx%5C+%5Ctextgreater+%5C+4)
Ответ: х∈(4;+∞).
УДАЧИ ВАМ ВО ВСЁМ)))!
=<span>№1
а) 8х²-16х+8=0,
8(х²-2х+1)=0.
8(х-1)²=0,
х-1=0
х=1
б) 20х²+20x+5=0
5(4·х² + 4·х +1)=0,
5(2х+1)²=0
2х+1=0
2х=-1,
х=-1/2
х=-0,5
в) 3х²-30х=0</span>
3х(х - 10)=0,
х=0 или х=10
№ 2
а)
![\frac{141 ^{3} +41 ^{3} }{182} -141\cdot 41= \frac{(141+41)(141 ^{2}-141\cdot 41+41 ^{2} ) }{182}-141\cdot41= \\ 141 ^{2} -2\cdot141\cdot 41+41 ^{2} =(141-41) ^{2}=100 ^{2} =10000](https://tex.z-dn.net/?f=+%5Cfrac%7B141+%5E%7B3%7D+%2B41+%5E%7B3%7D+%7D%7B182%7D+-141%5Ccdot+41%3D+%5Cfrac%7B%28141%2B41%29%28141+%5E%7B2%7D-141%5Ccdot+41%2B41+%5E%7B2%7D+%29+%7D%7B182%7D-141%5Ccdot41%3D+%5C%5C+141+%5E%7B2%7D++-2%5Ccdot141%5Ccdot+41%2B41+%5E%7B2%7D+%3D%28141-41%29+%5E%7B2%7D%3D100+%5E%7B2%7D+%3D10000+)
б)
![\frac{152 ^{3}+62 ^{3} }{214} -152\cdot 62= \frac{(152+62)(152 ^{2}-152\cdot62+62 ^{2} ) }{214} -152\cdot62= \\ 152 ^{2}-152\cdot62+62 ^{2} -152\cdot62= (152-62) ^{2}=90 ^{2}=8100](https://tex.z-dn.net/?f=+%5Cfrac%7B152+%5E%7B3%7D%2B62+%5E%7B3%7D++%7D%7B214%7D+-152%5Ccdot+62%3D+%5Cfrac%7B%28152%2B62%29%28152+%5E%7B2%7D-152%5Ccdot62%2B62+%5E%7B2%7D+%29+%7D%7B214%7D+-152%5Ccdot62%3D+%5C%5C+152+%5E%7B2%7D-152%5Ccdot62%2B62+%5E%7B2%7D+-152%5Ccdot62%3D+%28152-62%29+%5E%7B2%7D%3D90+%5E%7B2%7D%3D8100++)
Задача.
Витя красит за час 10/12 м³ забора, Костя 10/6 м³
Вместе они красят за час (10/12 + 10/6)=30/12 м³
10 : (30/12)=120/30=4 часа
за 4 часа покрасят забор Витя и Костя, работая вместе