(7х^2-5x+3)-(5x^2-4)=7x^2-5x+3-5x^2+4=2x^2-5x+7=(x-3,5)(x+1)
2x^2-5x+7=0
D=b^2-4ac(a=2, b=-5, c=7)
D=25+56=81=9^2
x1=5+9:4=14:4=3,5
ч2=5-9:4=-4:4=-1
X² - 18x + 45
Найдём корни
x² - 18x + 45 = 0
D/4 = 9² - 45 = 81 - 45 = 36
X1,2 = 9 + - √36 = 9 + - 6
X1 = 9+6 = 15
X2 = 9-6 = 3
x² - 18x + 45 = (x - 15)(x - 3)
Ctg(x/2 + π/8) = √3
x/2 + π/8 = π/6 + πk, k∈Z
x/2 = π/6 - π/8 + πk = π/24 + πk, k∈Z
x = π/12 + 2πk, k∈Z
No1
A=mgh=2000кг×10н/кг×2м=40000Дж=40КДж
No2
A=ngh=60кг×10н/кг×6м=3600Дж=3.6КДж