Question

Solve y = 2x - 4 by the substitution method.
7x – 5y = 14

Answer 1

Since you've already got " y equals ... something" in the first equation, substitute that into the second to solve for x.

y = 2x - 4
7x – 5y = 14

Take the first equation sub it into the first to get...

7x – 5y = 14
7x – 5() = 14
7x – 5(2x - 4 ) = 14

can you solve that last one now?

Answer 2

x=2 y=0

Answer 3

@Josh321 Usually instead of just giving the answer, we try to give students hints, and help them learn how to solve the problem themselves. :)

Answer 4

thankss!

Answer 5

fine
7x-5y=14
+5y +5y
7x=5y+14
-14 -14
7x-14=5y
7x-14=5(2x-4)
7x-14=10x-20
-7x -7x
-14=3x-20
+20 +20
6=3x
6/3=3x/3
2=x

y=2x-4
y=2(2)-4
y=4-4
y=0

Answer 6

the type box messed up lol

Answer 7

it's mushed

Answer 8

That is... quite a lengthy solution.

y = 2x - 4
7x – 5y = 14

Take the first equation sub it into the first to get...

7x – 5y = 14
7x – 5() = 14
7x – 5(2x - 4 ) = 14 distribute the 5 on the left
7x -10x +20 = 14 subtract 20 from both sides, and combine 7x with -10x
-3x = -6 divide by -3 on both sides
x = 2

Now substitute x = 2 into the first equation y = 2x - 4

y = 2x - 4
y = 2(2) - 4
y = 4-4
y = 0

done

x = 2
y = 4

and this agrees with the picture.
@coolaidd not sure if this is helpful, but there it is anyway. :)