If A = 
1
1
–2
2
1
–3
5
4
–9










, find | A |
7 Find values of x, if
(i)
2
4
2
4
5
1
6
x
x
=
(ii)
2
3
3
4
5
2
5
x
x
=
8 If 
2
6
2
18
18
6
x
x =
, then x is equal to
(A) 6
(B) ± 6
(C) – 6
(D) 0
4 3  Area of a Triangle
In earlier classes, we have studied that the area of a triangle whose vertices are
(x1, y1), (x2, y2) and (x3, y3), is given by the expression 1
2 [x1(y2–y3) + x2 (y3–y1) +
x3 (y1–y2)]