X- ширина,
(х+8) - длина
х*(х+8)=105
x^2 + 8*x -105 = 0
<span>Найдем дискриминант квадратного уравнения:
</span>D = b2 - 4ac = 82 - 4·1·(-105) = 64 + 420 = 484
x1 = (-8 - √484)/2 = (-8 - 22)/2 = -30/2 = -15
x2 =( -8 + √484)/2 =( -8 + 22)/2 = 14/2 = 7
<span>
7 см - ширина, 7+8 = 15 см - длина</span>
A1=1^3+1=2
a2=2^3+1=9
a3=3^3+1=28
a4=4^3+1=61
a5=5^3+1=126
a6=6^3+1=217
a7=7^3+1=344
Сos(t - 2π) = cos(2π - t) = cost
cos^2t = 1/(tg^2t + 1)
cos^2t = 1/(5/4 + 1)
cos^2t = 4/9
cost = -(2/3)
cost = (2/3)
ctg(-1) = - ctgt, tgt = -√5/2, tgt*ctgt = 1,ctgt = 1/tgt, ctgt = 1/(-√5/2)
sin(4π - t) = sint
sint = √(1 - cos^2x) = √[1 - (2/3)^2] = √5/3
( X + 3 ) / 4 - ( y + 2 ) / 2 = 0
X + 3 - 2( y + 2 ) = 0
X + 3 - 2y - 4 = 0
X = 2y + 1
3x + y = 1
3( 2y + 1 ) + y = 1
6y + 3 + y = 1
7y = - 2
y = - 2/7
X = 2•( - 2/7 ) + 1 = - 4/7 + 7/7 = 3/7
Ответ ( 3/7 ; - 2/7 )
2 1/3 -0.2*5= 2 1/3 -1=1 1/3