Verified answer

S = √(t² + 3t) + 1

S(1) = √(1 + 3) + 1 = 2 + 1 = 3

S(2) = √(4 + 6) + 1 = √10 + 1

S(3) = √(9 + 9) + 1 = √18 + 1 = 3√2 + 1

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S=3

3 = √(t²+3t) + 1

√(t²+3t) = 2

t²+3t - 4 = 0

D=9+16=25

t12=(-3+-5)/2 = - 4 1

t строго больше 0

t = 1