Maths-
General
Easy
Question
For the system of equations above, what is the value of x + y?
- -1
- 4
- 5
- 20
The correct answer is: 4
- Hint:
○ The concept used in the question is the concept of solving linear equations.
○ Given equations are linear equations in two variables.
○ Methods of Solving Linear Equations.
- Graphical Method
- Elimination Method
- Substitution Method
- Cross Multiplication Method
- Matrix Method
- Determinants Method
○ In the elimination method, any of the coefficients is first equated and eliminated. After elimination, the equations are solved to obtain the other equation.
- Step by step explanation:
○ Given:
2x - y = 8
x + 2y = 4
○ Step 1:
○ Let,
2x - y = 8 —------ eq.1
x + 2y = 4 —---------eq.2
○ Step 2:
○ Now equate coefficient of x
∴ multiply equation 2 by 2
[ x + 2y = 4 ] 2
2x + 4y = 8 —---- eq.3
○ Step 3:
○ Now subtract equation eq. 3 from eq.1
2x - y = 8
- 2x - 4y = - 8
—--------------------
-5y = 0
∴ y = 0
○ Step 4:
○ Put y = 0 in equation 1
2x - y = 8
2x - 0 = 8
2x = 8
x= 
x = 4
(x y) = ( 4,0 )
Therefore,
x + y = 4 + 0
x + y = 4
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