SOLUTION: if one of the roots of the equation 3x^2+19x+k=0 is -7 Find the value of k

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Question 1152321: if one of the roots of the equation 3x^2+19x+k=0 is -7 Find the value of k
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

if one of the roots of the equation 3x%5E2%2B19x%2Bk=0+is -7+
find the value of k
given: x=-7
3x%5E2%2B19x%2Bk=0+....substitute given root
3%28-7%29%5E2%2B19%28-7%29%2Bk=0+
3%2849%29%2B19%28-7%29%2Bk=0+
147-133%2Bk=0+
14%2Bk=0+
k=-14
=>3x%5E2%2B19x-14=0+
check:
3x%5E2%2B19x-14=0+.......factor
%28x+%2B+7%29+%283+x+-+2%29+=+0+-> as you can see, if %28x+%2B+7%29++=+0+=> x=-7