Question

2x + y = 7 5x + y = 9 Solve the system of equations.

Answer 1

Solvin by addition-elimination.
-(2x+y=7)
   5x+y=9
-------------------
     3x=2      ⇒x=2//3

  5*(2x+y=7)
-2*(5x+y=9)
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          3y=17    ⇒y=17/3

Solution: x=2/3; y=17/3

solving by equalization
2x+y=7     ⇒ y=7-2x
5x+y=9    ⇒ y=9-5x

7-2x=9-5x
-2x+5x=9-7
3x=2
x=2/3

y=7-2x
y=7-2*(2/3)
y=7 -  4/3  =  (21-4)/3=17/3

Solution: x=2/3 and y =17/3.

solving by substituion
2x+y=7    ⇒ y=7-2x

5x+(7-2x)=9
5x-2x=9-7
3x=2
x=2/3

y=7-2x
y=7- 2*(2/3)
y=7 -  4/3=(21-4) / 3=17/3

Solution: x=2/3 and y=17/3