Question

Solve the simultaneous equation
4x+7y=1
3x+10y=15

Answer 1

4x + 7y = 1
3x + 10y = 15

Multiply the first equation by -3, and the 2nd by 4.

-12x - 21y = -3
12x + 40y = 60

Add the equations:

19y = 57

y = 3

Plug this into any of the two equations to find 'x':

4x + 7y = 1

4x + 7(3) = 1

4x + 21 = 1

Subtract 21 to both sides:

4x = -20

Divide 4 to both sides:

x = -5

So our solution is (-5, 3)

Answer 2

4x + 7y = 1 ⇒ 12x + 21y = 3
3x + 10y = 15 ⇒ 12x + 40y = 60
-19y = -57
-19 -19
y = 3
4x + 7(3) = 1
4x + 21 = 1
- 21 - 21
4x = -20
4 4
x = -5
(x, y) = (-5, 3)