Найти все частичные пределы последовательности an = sin(πn/4)*|cos(πn/3)|^n
(0.2×3)2 = (2×0.2) × (3×2) = 0.4×6
А) 4/5=3/4x
16x=15
x=15/16
б) 8/9=1/2x
16x=9
x=9/16
в) 27/40=18x/25
40*18x=25*27
720x=675
x= 675/720= 135/144
г) x/4.5=2.1/0.63
0.63x=4.5*2.1
0.63x= 9.45
x=15
<span>1)
21x</span>²<span>=5x-1
</span>21x²-5x+1=0
D=b²-4ac
D = 25 - 4·21·1 = 25-84 = - 59
<span>Если D < 0, то действительных корней нет.
2)
x</span>²<span>-3x=0
</span>D=b²-4ac
D = 9 - 4·1·0 = 9
√D = √9 = 3
x₁ = (3+3)/2 = 6/2 = 3
x₂ = (3-3)/2 = 0/2 = 0
Ответ: {0; 3}
<span>3)
2x</span>²<span>-72=0
</span>D=b²-4ac
D = 0 - 4·2·(-72) = 576
√D = √576 = 24
x₁ = (0+24)/4 = 24/4 = 6
x₂ = (0-24)/4 = -24/4 = -6
Ответ: {-6; 6}
<span>4)
8x</span>²<span>-4=5x
8x</span>²-5x-4=0
D=b²-4ac
D = 25 - 4·8·(-4) = 25+128= 153
√D = √153
x₁ = (5+√153)/16
x₂ = (5-√153)/16
Ответ: {(5-√153)/16 ; (5+√153)/16 }<span>
5)
x</span>²<span>=18-3x
x</span>²+3x-18=0
D=b²-4ac
D = 9 - 4·1·(-18) = 9+72=81
√D = √81 = 9
x₁ = (-3+9)/2 = 6/2 = 3
x₂ = (-3-9)/2 = -12/2 = -6
Ответ: {-6; 3}<span>
6)
9y</span>²<span>+12y+4=0
</span>D=b²-4ac
D = 12² - 4·9·4 = 144-144=0 - один корень
√D = √0 = 0
y = (-12)/18 = - ²/₃
Ответ: - ²/₃
