3.Diketahui D(3,-6,1) dan E(m,4,-2) Jika panjang vektor DE sama dengan 11,hitunglah nilai m?

D(3, -6, 1)
E(m, 4, -2)
DE = e - d = (m, 4, -2) - (3, -6, 1) = (m - 3, 10, -3)

|DE| = 11
√(m - 3)² + (10)² + (-3)² = 11
m² - 6m + 9 + 100 + 9 = 121
m² - 6m + 118 = 121
m² - 6m - 3 = 0
m = 3 ± 2√3