tentukan unsur-unsur a=5,u3=11,s20=...
Matematika
Farhan29012001
Pertanyaan
tentukan unsur-unsur a=5,u3=11,s20=...
1 Jawaban
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1. Jawaban emida20
U3=11
a+2b=11
5+2b=11
2b=11-5
2b=6
b=3
Berarti
S20= n/2(2a+(n-1)b)
=20/2(2x5+(20-1)3)
=10(10+(19x3))
=10(10+57)
=10×67
=670