Bantuin jwb yg no.18 ya... jwbannya difoto aja trus kirim ke line aku aja Sarwendahlngg atau bbm ku lah 5137A4F8... Trimsss

proyeksi sklar = a.b/|b|
8 = (-2(0)+8(p)+4(4))/√(0²+p²+4²)
8 = (8p + 16)/√(p²+16)
1 = (p + 2) / √(p²+16)
√(p²+16) = p + 2
p² + 16 = (p + 2)²
p² + 16 = p² + 4p + 4
16 = 4p + 4
4p = 16 - 4
4p = 12
p = 12 / 4 = 3