а1=а4-3d
a1=-7-3*3=2
a8=a1+7d
a8=2+7*3=23
a₄= a₁ +3d
a₁ = a₄ - 3d
a₁ = -7 - 3×3 = -16
a₈=a₁+7d
a₈= -16 + 7×3 =5
ответ: a₁ = -16; a₈ = 5.
а1=а4-3d
a1=-7-3*3=2
a8=a1+7d
a8=2+7*3=23
a₄= a₁ +3d
a₁ = a₄ - 3d
a₁ = -7 - 3×3 = -16
a₈=a₁+7d
a₈= -16 + 7×3 =5
ответ: a₁ = -16; a₈ = 5.