Question

Solve the simultaneous equations 3x+y=8 X-3Y=11

Answer 1

Explanation:

let's organize our information :

• 3x+y=8
• x-3y=11

The trick here is to multiply x-3y=11 by -3 then add it to 3x+y=8 to get rid of x and get a normal equation

we get : -3x+9y= (-33)

then after the addition : 3x+y-3x+9y=8-33⇔ 10y=(-25)

so y=(-25)/10= -5/2

• let's replace y by -5/2 in 3x+y=8
• 3x-5/2 =8⇔ x= 21/6

so y= (-5/2) and x= 21/6

Answer 2

(7/2, -5/2)

Explanation:

We can solve this multiple ways: Algebraically (Substitution or Elimination) or Graphically

Step 1: Write 1st equation in terms of y

y = 8 - 3x

Step 2: Substitute y of 2nd equation

x - 3(8 - 3x) = 11

Step 3: Solve for x

x - 24 + 9x = 11

10x - 24 = 11

10x = 35

x = 7/2

Step 4: Plug x to find y

3(7/2) + y = 8

21/2 + y = 8

y = -5/2