Jawapan

2014-01-15T22:18:25+08:00
Hurm, yang ni kacang je nih.

x + y = 6
y = 6 - x     ---- 1

 x^{2} - xy + 4x = 7  ------ 2

Substitute 1 dlm 2.
 x^{2} - x(6 - x) + 4x = 7
 x^{2}  - 6x +  x^{2} + 4x = 7
 2x^{2} - 2x -7 = 0
( x - 2.436) ( x + 1.436) = 0
x = 2.436 or x = -1.436

When x = 2.436, y = 6 - 2.436
                         y = 3.564

When x = -1.436, y = 6 - (-1.436)
                          y = 7.436

2014-01-16T21:29:41+08:00