2) x² - 7x + 12 = 0
x₁ = 3 x₂ = 4 так как 3 + 4 = 7 , 3 * 4 = 12
4) x² + 8x + 7 = 0
x₁ = - 1 x₂ = - 7 так как - 1 - 7 = - 8 , - 1 * (- 7) = 7
6) x² + 2x - 15 = 0
x₁ = - 5 x₂ = 3 так как - 5 + 3 = - 2 , - 5 * 3 = - 15
7x=tg0
7x=0
x=0 наверно так
√ (3x^2 + 6x + 1) = 7 - x
3x^2 + 6x + 1 = x^2 - 14x + 49
2x^2 + 20x - 48 = 0 /:2
x^2 + 10x - 24 = 0
D= 100 + 4*24 = 100 + 96 = 196
x1 = ( - 10 + 14)/2 = 4/2 = 2
x2 = ( - 10 - 14)/2 = - 24/2 = - 12
1) x² + 12x + 27 = 0
D = 12² - 4*27 = 144 - 108 = 36
X1,2 = (- 12 + - √36)/2 = (- 12 + - 6)/2
X1 = (- 12 + 6)/2 = - 3
X2 = (- 12 - 6)/2 = - 9
Ответ : - 3; - 9
2) 8x² - 13x - 6 = 0
D = 13² - 4*(-6)*8 = 169 + 192 =361
X1,2 = (13 + - √361)/16 = (13 + - 19)/16
X1 = (13 + 19)/16 = 32/16 = 2
X2 = (13 - 19)/16 = - 6/16 = - 0, 375
Ответ: - 0,375; 2
1) d=a2–a1=7–2=5
a10=a1+9d=2+9•5=47
2) d=a2–a1=–28+30=2
a28=a1+27d=–30+27•2=24
3) d=a2–a1=8–2=6
Сумму каких? Двух? Пяти? 25?))
S2=2+8=10
S5=(2a1+4d)/2•5=(2•2+4•6)/2•5=70
S25=(2a1+24d)/2•25=(2•2+24•6)/2•25=1850
4) b2=2; q=1/2; n=6
b1=b2:q=2:1/2=4
b6=b1•q^5=4•1/32=1/8
S6=(b6•q–b1)/(q–1)=(1/8•1/2–4)/(1/2–1)
= (-63/16)/(-1/2) = (63•2)/16=63/8=
=7 7/8
5) S7=210; a1=2
S7=(2a1+6d)/2•7=(4+6d)/2•7=
=(2+3d)•7=14+21d
14+21d=210
21d=196
d=196:21=9 1/3
