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A. Sistem Pertidaksamaan Linear

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86<br />

Jawab:<br />

a. U 2 + U 4 = 40<br />

(a + b) + (a + 3b) = 40<br />

2a + 4b = 40<br />

a + 2b = 20 . . . . (1)<br />

U + U 3 5<br />

(a + 2b) + (a + 4b)<br />

=<br />

=<br />

46<br />

46<br />

2a + 6b = 46<br />

a + 3b = 23 . . . . (2)<br />

Dari (1) dan (2) diperoleh:<br />

a + 2b = 20<br />

a + 3b = 23<br />

–b = –3<br />

b = 3<br />

Nilai b disubstitusikan ke dalam persamaan (1)<br />

a + 2b = 20<br />

a + 2(3) = 20<br />

a + 6 = 20<br />

a = 14<br />

Jadi, a = 14 dan b = 3.<br />

b. Un U 2<br />

= a + (n – 1)b<br />

= 14 + (2 – 1)3<br />

= 14 + 3<br />

= 17<br />

U 3 = 14 + (3 – 1)3<br />

= 14 + 2(3)<br />

= 14 + 6<br />

= 20<br />

U 6 = 14 + (6 – 1)3<br />

= 14 + 5(3)<br />

= 14 + 15<br />

= 29<br />

U 2 + 1<br />

2 U 3 + U 6<br />

= 17 + 1<br />

(20) + 29<br />

2<br />

= 17 + 10 + 29<br />

= 56<br />

Jadi, nilai U + 2 1<br />

2 U3 + U = 56. 6<br />

b. Suku Tengah Barisan Aritmetika<br />

Barisan aritmetika yang jumlah sukunya ganjil dan minimal terdiri<br />

dari 3 suku memiliki suku tengah (U ).<br />

t<br />

Matematika SMA/MA Kelas XII Program Bahasa

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