Question 654294

Hi. My problem is: Solve the linear system by using elimination 
So
7x - 4y = -30
3x + 4y = 10

I tried                    


7x - 3•-2 
3x. -6 + 4y = 10
10x = -20 = (-2, ).   +6.    +6
4y = 16 / 4 = 4 ??? Am I performing this correct? Please help. Final answer is (-2,4)


No, you're not!!


7x  - 4y = - 30 ---- eq (i)
3x + 4y = 10 ------ eq (ii)
10x = - 20 ----- Adding eqs (ii) & (i) to eliminate y and determine value of x


x = {{{(- 20)/10}}}, or {{{highlight_green(- 2)}}}


7(- 2) - 4y = - 30 ----- Substituting - 2 for x in eq (i)
- 14 - 4y = - 30
- 4y = - 30 + 14
- 4y = - 16
y = {{{(- 16)/- 4}}}, or {{{highlight_green(4)}}}


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