Question

Solve the simultaneous equations by substitution
3x+5y=−4
3x+7y=4

Answer 1

x
=
−
3

y
=
5
Step-by-step explanation:
I would multiply the first equation by
−
4
and the second by
3
and add together the two equatins (in columns):
{
−
12
x
−
28
y
=
−
104

{
12
x
+
15
y
=
39

0
−
13
y
=
−
65

So:
y
=
65
13
=
5

Substitute back this value into the first equation:
3
x
+
7
⋅
5
=
26

3
x
=
26
−
35
=
−
9

x
=
−
9
3
=
−
3

Answer 2

(x,y) (12, -8)

Hope it helps!