I need help. tomorrow i have my state test.

Please help, super hard question for me!

dem82 [27]

Answer:

Step-by-step explanation:

When using the substitution method we use the fact that if two expressions y and x are of equal value x=y, then x may replace y or vice versa in another expression without changing the value of the expression.

Solve the systems of equations using the substitution method

{y=2x+4

{y=3x+2

We substitute the y in the top equation with the expression for the second equation:

2x+4 = 3x+2

4−2 = 3x−2

2=== = x

To determine the y-value, we may proceed by inserting our x-value in any of the equations. We select the first equation:

y= 2x + 4

We plug in x=2 and get

y= 2⋅2+4 = 8

The elimination method requires us to add or subtract the equations in order to eliminate either x or y, often one may not proceed with the addition directly without first multiplying either the first or second equation by some value.

Example:

2x−2y = 8

x+y = 1

We now wish to add the two equations but it will not result in either x or y being eliminated. Therefore we must multiply the second equation by 2 on both sides and get:

2x−2y = 8

2x+2y = 2

Now we attempt to add our system of equations. We commence with the x-terms on the left, and the y-terms thereafter and finally with the numbers on the right side:

(2x+2x) + (−2y+2y) = 8+2

The y-terms have now been eliminated and we now have an equation with only one variable:

4x = 10

x= 10/4 =2.5

Thereafter, in order to determine the y-value we insert x=2.5 in one of the equations. We select the first:

2⋅2.5−2y = 8

5−8 = 2y

−3 =2y

−3/2 =y

y =-1.5

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2 years ago