SOLUTION: First let me say I'm an old guy (52 years old)! Here is my problem, my 25 year old daughter has challenged me to solve this problem: What is the sum of the solution of the equ

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: First let me say I'm an old guy (52 years old)! Here is my problem, my 25 year old daughter has challenged me to solve this problem: What is the sum of the solution of the equ      Log On


   

Question 21992: First let me say I'm an old guy (52 years old)!
Here is my problem, my 25 year old daughter has challenged me to solve this problem:
What is the sum of the solution of the equation 3x^2 + 11x = 4 (three x squared plus 11x equals four
She gave me the answer as negative three and two-thirds, and has challenged me to show how she arrived at this answer.
Quite frankly, I have no idea. Any help would be greatly appreciated!
Thanks,
"Old Guy Dad"

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Well, hang in there "old man"! (I'm 73!)
First, let's find the solutions or roots, as they are commonly called.
3x%5E2+%2B+11x+=+4 First subtract 4 from both sides of the equation.
3x%5E2+%2B+11x+-+4+=+0 Solve this quadratic equation by factoring.
%283x+-+1%29%28x+%2B+4%29+=+0 Now apply the zero product principle.
%283x+-+1%29+=+0 and/or %28x+%2B+4%29+=+0
If 3x+-+1+=+0 then, 3x+=+1 and x+=+1%2F3
If x+%2B+4+=+0 then, x+=+-4
The roots are:
x+=+1%2F3
x+=+-4
So their sum is:
1%2F3+-+4 = -3 1/3
Your daughter is correct!