1.
2x^2-11x+12=0
D=121-96=25
x1=(11+5)/4=4
x2=(11-5)/4=1,5
2.
-3x^2-x+8=x^2-6x+9
-4x^2+5x-1=0
4x^2-5x+1=0
D=25-16=9
x1=(5+3)/8=1
x2=(5-3)/8=0,25
3.
-x^2+3x+55=x^2+14x+49
-2x^2-11x+6=0
2x^2+11x-6=0
D=121+48=169
x1=(-11+13)/4=0,5
x2=(-11-13)/4=-6
(3*5*7)*1+2=107
(3*5*7)*2+2=212
(3*5*7)*3+2=317
(3*5*7)*4+2=422
(3*5*7)*5+2=527
(3*5*7)*6+2=632
(3*5*7)*7+2=737
(3*5*7)*8+2=842
(3*5*7)*9+2=947
Ответ: 212, 422, 737.
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a₆ + a₁₀ - (a₃ + a₈) = 15
a₁ + 5d + a₁ + 9d - a₁ - 2d - a₁ - 7d = 15
5d = 15
d = 3