halo adakah yg bisa membantu saya

<p>U_7 = a+(n-1)b = 47</p><p>U_4 = a+(n-1)b = 26&nbsp;</p><p>a+6b=47&nbsp;</p><p>a+3b=26&nbsp;</p><p>3b=21&nbsp;</p><p>b=7&nbsp;</p><p>*Substitusi ke persamaan</p><p>a+3(7)=26</p><p>a=5&nbsp;</p><p>{rumus suku ke-n} = 5+(n-1)7&nbsp;</p><p>{suku ke-30} = 5+(30-1)7</p><p>&nbsp;= 5+203&nbsp;</p><p>= 208&nbsp;</p><p>U_n = 313&nbsp;</p><p>313 = 5+(n-1)7&nbsp;</p><p>313 = 5+7n-7&nbsp;</p><p>7n-7 = 313-5&nbsp;</p><p>7n = 313-5+7&nbsp;</p><p>7n = 315&nbsp;</p><p>n = 45</p><p>&nbsp;</p><p>Semoga membantu ^^</p>