11.
3x - 2y = 2
5x - 5y = 10
We can divide the second one by 5,
x - y = 2
and multiply by 2,
2x - 2y = 4
Subtracting from the first equation,
3x - 2y - (2x - 2y) = 2 - 4
x = -2
y = x - 2 = -4
Check:
3x - 2y = 3(-2) - 2(-4) = -6 + 8 = 2 good
5x - 5y = 5(-2) - 5(-4) = -10 + 20 = 10 good
Answer: x=-2, y=-4
12. Factor
First we take out the common factor of 2. Then we need two numbers that add to 11 and multiply to 30; that's 5 and 6.
[tex]2k^2 + 22k + 60 = 2(k^2 + 11k + 30)=2(k+5)(k+6)[/tex]
Answer: 2(k+5)(k+6)
13.
5x+3y = -15 Solve for x given y=0
5x+3(0)=-15
5x = -15
x = -15/5 = -3
Answer: -3
