solve the system by elimination?

Question

a) x + 9y =-63
-3x + 10y = -70

b) -4x - 7y = -17
2x - 3y = -11

Answer 1

(a) multiplying the first equation by 3 you get:
3x + 27y = -189
-3x + 10y = -70

therefore (if you add the equations together)

37y = -259

solve for y, re-substitute and solve for x


(b) multiplying the second equation by 2 you get:
-4x -7y = -17
4x - 6y = -22

therefore (if you add the equations together)

-13y = -39

solve for y, resubstitute and solve for x

Answer 2

a) x + 9y = -63 multiply this one by 3 to get rid of the x
-3x + 10y = -70 multiply this one by 1

3x + 27y = -189
-3x + 10y = -70 add both lines

37y = -259
y = -7

sub y= -7 into first equation to solve for x

x + 9(-7) = -63
x = -63 + 63
x = 0

check in equation 2
-3(0) + 10(-7) = -70
0 -70 = -70
0 = 0

b) -4x - 7y = -17
2x - 3y = -11 multiply this one by 2 to get rid of the x

-4x - 7y = -17
4x - 9y = -22 add both lines

-16y = -39 solve for y
y = 2.4375

sub y=2.4375 into first equation

-4x - 7(2.4375) = -17
-4x = 0.0625
x = -0.015625

check in equation 2

2(-0.015625) - 3(2.4375) = -11

i have to go, ill finish this later

Answer 3

You need to solve 1 equation for 1 variable and substitute this expression for that result into the 2nd equation. These are easy, try them. Hint: y=-269/37 in the first problem.

Try the 2nd one - email me if you can't get it @ [e-mail] and I'll write it out and email the steps to you.