23.4k views
3 votes
3. Solve this system by elimination

-5x - 10y = 20
-5x - 8y = 14
6. Solve this system by substitution
x = 4
-4x - 5y = 4

User Tosca
by
8.0k points

1 Answer

2 votes

Answer:

3. (-4/5, -3) 6. (4, 12/-5)

Explanation:

3. so first we have

-5x - 10y = 20

-5x - 8y = 14

so first we have to have the x's be opposite so we multiply the top one by -1 which gets us

5x + 10y = -20

-5x - 8y = 14

then we cancel out the x's and subtract 10 by 8 and -20 by 14 so it's now

2y = -6

then we divide by 2 on both sides so it's

y = -3

but now we have to solve for x so we substitute y in on the bottom equation so now it is

-5x - 8(-3) = 20

now we multiply

-5x + 24 = 20

subtract 24 from both sides

-5x = -4

divide by -5

x = -4/5

then put it in coordinates

(-4/5, -3)

6. so we have

x = 4

-4x - 5y = 4

so first we have to substitute the top in for the bottom so now we have

-4(4) - 5y = 4

distribute

-8 - 5y = 4

add 8 to both sides

-5y = 12

divide

y = 12/-5

coordinates

(4, 12/-5)

User ABarrier
by
7.9k points