Answer:
x= -3
Explanation:
Solve the following system:
{8 y + 4.2 x = 41.8
y - 4.2 x = 19.4
In the second equation, look to solve for y:
{8 y + 4.2 x = 41.8
y - 4.2 x = 19.4
y - 4.2 x = y - (21 x)/5 and 19.4 = 97/5:
y - (21 x)/5 = 97/5
Add (21 x)/5 to both sides:
{8 y + 4.2 x = 41.8
y = 1/5 (21 x + 97)
Substitute y = 1/5 (21 x + 97) into the first equation:
{4.2 x + 8/5 (21 x + 97) = 41.8
y = 1/5 (21 x + 97)
4.2 x + (8 (21 x + 97))/5 = ((168 x)/5 + 776/5) + 4.2 x = 37.8 x + 776/5:
{(37.8 x + 776/5) = 41.8
y = 1/5 (21 x + 97)
In the first equation, look to solve for x:
{37.8 x + 776/5 = 41.8
y = 1/5 (21 x + 97)
37.8 x + 776/5 = (189 x)/5 + 776/5 and 41.8 = 209/5:
(189 x)/5 + 776/5 = 209/5
Subtract 776/5 from both sides:
{(189 x)/5 = -567/5
y = 1/5 (21 x + 97)
Multiply both sides by 5/189:
{x = -3
y = 1/5 (21 x + 97)
Substitute x = -3 into the second equation:
Answer: {x = -3, y = 34/5