Matematika

Pertanyaan

U2 =15, U4=135, U5= ?, S3=?
tolong dibantu :)

1 Jawaban

  • u2= a+b = 15
    u4= a+3b = 135
    ________ -
    -2b= -120
    b= 60

    Substitusi b=60
    a+b =15
    a+60=15
    a = -45

    Maka
    U5= a+4b
    = -45+4(60)
    = -45+240
    = 195

    Maka s3= n/2(2a+(n-1)b)
    = 3/2(2(-45)+2(60))
    = 3/2(-90+120)
    = 3/2(30)
    = 45


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