06 Kunci Jawaban dan Pembahasan MAT IX
06 Kunci Jawaban dan Pembahasan MAT IX
06 Kunci Jawaban dan Pembahasan MAT IX
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10. <strong>Jawaban</strong>: d<br />
Un = 2n2 – 5n<br />
U8 = 2 × 82 – 5 × 8 = 128 – 40 = 88<br />
U9 = 2 × 92 – 5 × 9 = 162 – 45 = 117<br />
U8 + U9 = 88 + 117 = 205<br />
11. <strong>Jawaban</strong>: b<br />
(3x – 4)(2x + 1)<br />
= 3x(2x + 1) – 4(2x + 1)<br />
= 6x2 + 3x – 8x – 4<br />
= 6x2 – 5x – 4<br />
12. <strong>Jawaban</strong>: c<br />
2<br />
2<br />
x − 3x −10<br />
=<br />
x − 8x + 15<br />
(x 5)(x 2) − +<br />
(x − 5)(x − 3)<br />
13. <strong>Jawaban</strong>: c<br />
= x 2<br />
+<br />
x − 3<br />
m+ n m+ n n(m + n) + m(m + n)<br />
+ =<br />
m n<br />
mn<br />
=<br />
=<br />
=<br />
2 2<br />
mn + n + m<br />
mn<br />
+ mn<br />
2 2<br />
m + 2mn+ n<br />
mn<br />
104 <strong>Kunci</strong> <strong>Jawaban</strong> <strong>dan</strong> <strong>Pembahasan</strong> PR Matematika Kelas <strong>IX</strong><br />
2<br />
(m + n)<br />
mn<br />
14. <strong>Jawaban</strong>: d<br />
3x + 14 = 6 – x<br />
⇔ 3x + x = 6 – 14<br />
⇔ 4x = –8<br />
⇔ x= –2<br />
⇔ x – 2 = –2 – 2<br />
= –4<br />
15. <strong>Jawaban</strong>: c<br />
P = {2, 3, 5, 7, 11}<br />
Q = {1, 2, 3, 4, 6, 12}<br />
P ∪ Q = {1, 2, 3, 4, 5, 6, 7, 11, 12}<br />
16. <strong>Jawaban</strong>: a<br />
M = siswa suka Matematika<br />
B = siswa suka Bahasa Inggris<br />
n(M ∪ B) = n(M) + n(B) – n(M ∩ B)<br />
= 25 + 23 – 15 = 33<br />
Jumlah siswa = n(M ∪ B) + n((M ∪ B) C )<br />
= 33 + 7 = 40 anak.<br />
17. <strong>Jawaban</strong>: a<br />
2 satu lebihnya dari 1<br />
4 satu lebihnya dari 3<br />
6 satu lebihnya dari 5<br />
8 satu lebihnya dari 7<br />
Jadi, relasi yang tepat yaitu ”satu lebihnya dari”.<br />
18. <strong>Jawaban</strong>: a<br />
f : x → 7 – 4x2 maka f(x) = 7 – 4x2 f(0) = 7 – 4 × 02 = 7<br />
f(1) = 7 – 4 × 12 = 3<br />
f(2) = 7 – 4 × 22 = –9<br />
f(3) = 7 – 4 × 32 = –29<br />
f(4) = 7 – 4 × 42 = –57<br />
Jadi, himpunan pasangan berurutannya {(0, 7), (1,<br />
3), (2, –9), (3, –29), (4, –57)}.<br />
19. <strong>Jawaban</strong>: c<br />
x − 1 y − 2<br />
+ = –2<br />
2 4<br />
⇔ 2(x – 1) + y – 2 = –8<br />
⇔ 2x – 2 + y – 2 = –8<br />
⇔ 2x + y = –4 . . . (i)<br />
4x + 1 3y − 2<br />
– = 1<br />
3 4<br />
⇔ 4(4x + 1) – 3(3y – 2) = 12<br />
⇔ 16x + 4 – 9y + 6 = 12<br />
⇔ 16x – 9y = 2 . . . (ii)<br />
Eliminasi x dari (i) <strong>dan</strong> (ii):<br />
8 × (i) : 16x + 8y = –32<br />
(ii) : 16x – 9y = 2<br />
––––––––––––– –<br />
17y = –34 ⇔ y = –2<br />
Substitusi y = –2 ke (i):<br />
2x – 2 = –4 ⇔ 2x = –2<br />
⇔ x= –1<br />
Nilai x – y = –1 – (–2) = 1.<br />
20. <strong>Jawaban</strong>: c<br />
x = uang Budi<br />
y = uang Rini<br />
3 1<br />
x – y = 5.500<br />
4 2<br />
⇔ 3x – 2y = 22.000 . . . (i)<br />
2 2<br />
x + y = 26.000<br />
3 5<br />
⇔ 10x + 6y = 390.000 . . . (ii)<br />
Eliminasi y dari (i) <strong>dan</strong> (ii):<br />
3 × (i) : 9x – 6y = 66.000<br />
(ii) : 10x + 6y = 390.000<br />
–––––––––––––––– +<br />
19x = 456.000 ⇔ x = 24.000<br />
Substitusi x = 24.000 ke (i):<br />
3 × 24.000 – 2y = 22.000<br />
⇔ 72.000 – 2y = 22.000<br />
⇔ 2y = 50.00<br />
⇔ y = 25.000<br />
Jumlah uang Budi <strong>dan</strong> Rini<br />
= x + y<br />
= Rp24.000,00 + Rp25.000,00<br />
= Rp49.000,00