So when it intersects the x-axis, y = 0.awilhelm wrote:Please help with the following question:
In the xy-plane, at what two points does the graph of y = (x + a)(x + b) intersect the x-axis?
1) a + b = -1
2) The graph intersects the y-axis at (0, -6)
Thanks!
0 = (x+a)(x+b)
x = -a or x = -b
Statement (1)
a + b = -1
A and B could be multiple values....INSUFFICIENT
Statement (2)
The graph intersects the y-axis at (0, -6)
y = (x + a)(x + b)
-6 = (0+a)(0+b)
-6 = ab
A and B could be multiple values...INSUFFICIENT
St (1) and St (2)
a + b = -1
-6 = ab
-6 = (-1 - b)*b
-6 = -b - b^2
b^2+b-6 = 0
b= -3 or b = 2
If b = -3, then a = 2
If b = 2, then a = -3
y = (x+2)(x-3) or
y= (x-3)(x+2)
SUFFICIENT (C)
