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3 votes
Solve the system of equations.


​−5x+4y=3

​x=2y−15
​​
x equals

y equals

2 Answers

1 vote

Answer:

Solve the system of equations.

5

x

+

4

y

=

3

x

=

2

y

15

−5x+4y=3

x=2y−15

Explanation:

We are given that

x

=

2

y

15

x=2y−15start color #6495ed, x, end color #6495ed, equals, start color #6495ed, 2, y, minus, 15, end color #6495ed. Let's substitute this expression into the first equation and solve for

y

yy as follows:

5

x

+

4

y

=

3

5

(

2

y

15

)

+

4

y

=

3

10

y

+

75

+

4

y

=

3

6

y

=

72

y

=

12

−5x+4y

−5⋅(2y−15)+4y

−10y+75+4y

−6y

y

=3

=3

=3

=−72

=12

Hint #22 / 3

Since we now know that

y

=

12

y=12start color #ff00af, y, end color #ff00af, equals, start color #ff00af, 12, end color #ff00af, we can substitute this value in the second equation to solve for

x

xx as follows:

x

=

2

y

15

x

=

2

12

15

x

=

9

x

x

x

=2⋅y−15

=2⋅12−15

=9

Hint #33 / 3

This is the solution of the system:

x

=

9

y

=

12

x=9

y=12

X= 9

y= 12

User Amitayh
by
5.7k points
5 votes
Note: in the 2nd eqn we are given a formula for x: x = 2y-15. Sub this result into the first eqn; doing so will eliminate x:

-5(2y-15)+4y =3

-10y + 75 + 4y = 3, so -6y = -72. Then y = 12. Solution is (9,12).

Check this by subst.:

Is -5(9)+4(12) = 3?
Is -45 + 48 = 3? YES.

User Flat
by
5.2k points