Solve the Linear Equations

Nov 2015
246
4
hyderabad
I tried to solve the equations in different ways but unsuccessful. Kindly someone solve this :

If $a, b, c$ and $d$ satisfy the equations

$a + 7b + 3c + 5d = 16$

$8a + 4b + 6c + 2d = −16$

$2a + 6b + 4c + 8d = 16$

$5a + 3b + 7c + d = −16$

Then $ (a + d)(b + c)$ equals to ?

Thank you in Advance!!!
 

skipjack

Forum Staff
Dec 2006
21,478
2,470
The equations are satisfied by a = c = -2, b = d = 2.
 

Denis

Math Team
Oct 2011
14,592
1,026
Ottawa Ontario, Canada
I want to know how to solve these... Please let me know the steps.
Google "solving 4 unknowns with 4 equations"

Can't teach from here...no blackboard:)