Wyznacz pierwszy wyraz i różnicę ciągu arytmetycznego an gdy dane są a1+ a5 = 16, a1* a5 = 28
a₅=a₁+4r
a₁+a₁+4r=16
a₁(a₁+4r)=28
2a₁+4r=16/;2
a₁=8-2r
...............
(8-2r)(8-2r+4r)=28
(8-2r)(8+2r)=28
64-4r²=28
64-28=4r²
r²=36;4
r=√9
r=3 lub r=-3
............................
a₁=8-2×3=2 lub a₁=8-2×(-3)=14
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a₅=a₁+4r
a₁+a₁+4r=16
a₁(a₁+4r)=28
2a₁+4r=16/;2
a₁=8-2r
...............
(8-2r)(8-2r+4r)=28
(8-2r)(8+2r)=28
64-4r²=28
64-28=4r²
r²=36;4
r=√9
r=3 lub r=-3
............................
a₁=8-2×3=2 lub a₁=8-2×(-3)=14