I

I

Multiply (1) by 1-1, (2) by, and subtract;

α C

Adding (2) and (3) we get, -4x + 7y = 22.........(4),

from (1) 3-7y+42 = 1,
from (3) 4x-8y +4z = 0;

3.

From (1), (26x + 132 − 52) + (36y — 72z +12) = 39x — 78, whence 13x-36y +592 = 38,

from (3), 13-117y+ 3512 = 234;

From (2),

.. 2922 — 81y = 196 ....................... (4).

(126x-84y+210)-(120x-150y+2102)=60+(1053-3152+210),

whence 6x-39y+ 1052 = 60;

or 2x-13y+ 35% = 20,

and from (3), 2x-18y + 54% = 36;

.. 192-5y = 16;

.. 19 × 2922- 1460y=4672,

and from (4), 19 × 2922- 1539y=3724;

.. 79y=948, or y = 12;

16+5y 19

= = 4, and x 18+9y — 272 = 18.

13. xy=3(x+y), xz = 8(x+2), 7yz=9(y + z), find x, y, z.

71

=

144

I

-

subtract (2), = (−3+3)=7; -7

У

8

7

9