x2 – 9x+k = 0 , dengan akar-akar p dan q
p+q = 9 → p = 9 – q
p, q, (p+q+3) Membentuk barisan Geometri
q2=p.12
q2=(9–q).12
q2+12q–12.9=0
(q+18)(q–6)=0
q=–18 atau q=6
| * | Untuk q = –18 → p = 27 | |
| |p–q|=|27-(-18)|=45 | ||
| * | Untuk q = –18 → p = 27 | |
| |p-q|=|3-(6)|=3 |
no.22
1/2 log(2x-1)≥ 1/4 log x
2-1 log(2x-1)≥ 2-2 log x
- 2log(2x-1)≥(-1/2)2log x
2 2log(2x-1)≤ 2log x
(2x-1)2 ≤ x
4x2 - 5x + 1 ≤ 0
(x-1)(4x-1) ≤0
no.23
a=3, r=2, dan S(n+2) = 381
no.24
Sehingga:
no.25
f(x)=2x
Sehingga:
| f(x)+f(x+1)+f(x+2)+f(x+3) | = | 2x + 2x+1+ 2x+2+ 2x+3 |
| = | 2x+ 2.2x+ 4.2x+ 8.2x | |
| = | (1+2+4+8)2x | |
| = | 15.2x | |
| = | 15.f(x) |