Mohon bantuannya .. #makasih ..

15.
9x² - 16 = (3x + 4)(3x - 4)
3x² + 2x - 8 = (3x - 4)(x + 2)

Jawab = (3x + 4) / (x + 2)

16.
1/2 (X+3) = 12 - 2/3X
1/2 (X+3) = 36/3 - 2/3X
1/2 (X+3) = 1/3 (36 - 2X)
3 (X+3) = 2 (36 - 2X)
3X + 9 = 72 - 4X
7X = 63
X = 9

X + 2 = 9 + 2 = 11

17.
Deret bilangan aritmatika
a = x
b = 2 (bilangan ganjil berurutan)


Sn = 1/2 n (2a + (n-1)b)
S3 = 1/2 3 (2x + (3-1)2)
105 = 3/2 (2x + 4)
105 = 3x + 6