| Quadratic Equation Problem | 6:59 AM |
|
Filed under:
chemistry
|
|
One student make a mistake in copying the coefficient of x and got a root of +3 and -2. Another student made a mistake in copying the constant term and got a root of +3 and +2. Find the correct equation and correct roots.
Solution:
Let the correct equation be:
Ax^2 + Bx + c
and the correct roots be:
x1 and x2
Consider the first student's equation. It is wrong in B but correct in A and C. Thus,product of roots is the same as that of the correct equation.
C/A = 3(-2)= -6
Consider the 2nd student's equation. It is wrong in C but correct in A&B.Thus,sum of roots is the same as that of the correct equation.
-B/A = 3 + 2
B/A = -5
Consider the correct equation:
Ax^2 + Bx + c = 0 ------> divide by A
x^2 + B/Ax + C/A =0
thus
x^2-5x-6=0 -------> correct equation
solve for roots by factoring:
x^2-5x-6=0
(x-6)(x+1)=0
x=6 and -1
Therefore,the correct roots are:
6 and -1


0 comments:
Post a Comment
Post a Comment