− 24
Explanation:
Here, a1 = 4, b1 = 3, c1 = 19
a2 = 4, b2 = -3, c2 = -11
∴ Dx = `|(c_1, b_1),(c_2, b_2)| = |(19, 3),(-11, -3)|`
= -57 + 33
= -24