tolong bantu jawab kak dengan cara
Barisan Dan DEret
Geometri
Penjelasan dengan langkah-langkah:
Barisan geometri
u₆ = 2
u₃ = - 16
s₇ = . . .
[tex]\sf \dfrac{u_6}{u_3} = \dfrac{2}{-16}\\[/tex]
[tex]\sf r^{6-3} = -\dfrac{1}{8}[/tex]
[tex]\sf r^{3} = (-\frac{1}{2})^3[/tex]
[tex]\sf r = -\frac{1}{2}[/tex]
u₃ = -16
ar² = - 16
[tex]\sf a(-\frac{1}{2})^2 = - 16\to a= -64[/tex]
r = - 1/2 ---> r < 1 , maka
[tex]\sf s_n = \dfrac{a(1 - r^n)}{1 - r}[/tex]
[tex]\sf s_7 = \dfrac{-64(1 - (-\frac{1}{2})^7)}{1 - (-\frac{1}{2})}[/tex]
[tex]\sf s_7 = \dfrac{-64(1 +\frac{1}{128})}{\frac{3}{2}}[/tex]
[tex]\sf s_7 = \dfrac{-64 -\frac{1}{2}}{\frac{3}{2}}[/tex]
[tex]\sf s_7 = \dfrac{-128 -1}{3} = -\frac{129}{3} = - 43[/tex]
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