Suku deret aritmatika diketahui U1=11 dan U7=27 tentukan a suku pertama dan suku ke 25

U1 a=11
U7 a+6b=27

disubtitusi

11+6b=27
6b=16
b=8/3

U25= a+(n-1)b
11+(24)8/3
11+64
75

semoga membantu

U₁ = 11
a = 11

U₇ = a + 6b
27 = 11 + 6b
27 - 11 = 6b
16 = 6b
[tex]b = \frac{16}{6} = \frac{8}{3} [/tex]

Un = a + ( n - 1 ) b
U₂₅ = 11 + ( 25 - 1 ) 8/3
U₂₅ = 11 + 24( 8/3 )
U₂₅ = 11 + 8( 8 )
U₂₅ = 11 + 64
U₂₅ = 75