<span>а1=6 а14=-7</span>
<span>a14 = a1 + d*(14 - 1)</span>
<span>-7 = 6 + d*13</span>
<span>13d = -7 -6 = -13</span>
<span>d = -1</span>
<span>ОТВЕТ -1</span>
d=(a14-a1)/13=(-7-6)/13=-1
воть))))))) на фото все понятно