Question

6x-5y=9

-18x+by=-27
What value of b will make the system of equations above have infinitely many solutions?

Answer 1

6x-5y=9

*3 *3

18x-15y=27

-18x+by=-27

we sum these equation

0+(b-15)y=0

b-15=0

b=15

Explanation:

Answer 2

6x-5y=9.....
Slope = 2.400/2.000 = 1.200
x-intercept = 9/6 = 3/2 = 1.50000
y-intercept = 9/-5 = -1.80000
So -18+1.8b=-27
Slope = 10
x-intercept = 15/10 = 3/2 = 1.50000
b-intercept = 15/-1 = -15.00000