SOLUTION: Find the value of k on x^2+3x+k-1=0 if the quadratic equation has: a) equal roots b) one root -3 thanks :)

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Question 357829: Find the value of k on x^2+3x+k-1=0 if the quadratic equation has:
a) equal roots
b) one root -3
thanks :)
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
a)Use the discriminant.
D=b%5E2-4ac
D=3%5E2-4%281%29%28k-1%29
For equal roots,
D=0
9-4%28k-1%29=0
4%28k-1%29=9
k-1=9%2F4
k=9%2F4%2B4%2F4
k=13%2F4
.
.
.
b) Use the quadratic formula,
x+=+%28-3+%2B-+sqrt%28+9-4%28k-1%29+%29%29%2F%282%29=-3+
.
.
-3+%2B-+sqrt%28+9-4%28k-1%29+%29%29=-6+
.
.
0+%2B-+sqrt%28+9-4%28k-1%29+%29%29=-3+
.
.
sqrt%28+9-4%28k-1%29+%29%29=3+
.
.
+9-4%28k-1%29=9+
.
.
-4%28k-1%29=0
.
.
highlight%28k=1%29
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.
.
x%5E2%2B3x=0
.
.
.