3x – y = 7; x + 4y = 11

(i) 3x – y = 7; x + 4y = 11


Sol. 3x – y = 7;  x + 4y = 11


D
=
3
-1
=
(3 × 4) – (1 × - 1)
=
12 + 1
=
13


1
4









DX
=
7
-1
=
(7 × 4) – (11 × -1)
=
28 + 11
=
39


11
4









DY
=
3
7
=
(3 × 11) – (1 × 7)
=
33  - 7
=
26


1
11









By Cramer's rule,


x
=
Dx
=
39
=
3


D

13





y
=
Dx
=
26
=
2


D

13






x = 3 and y = 2 is the solution of given simultaneous equations.

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