To solve ax*x+bx+c =
0.
Solution: We can write the equation
like:
ax^2+bx+c= 0.....(1), as x*x = x^2. This is a second
degree equation and is also called a quadratic equation which will be solved by writing
the left as diffrence of an unknown square and a known square equal to
zero:
LHS of (1) :
ax^2+bx+c =
a[x^2+(b/a)x]+c
=a(x^2+(b/a)x+(b/(2a))^2] - b^2/(4a)+c.
Here (b^2/(4a) is added and subtracted.
=a[x+(b/(2a))]^2 -
(b^2-4ac)/4a .
=a{[x+b/(2a)]^2 -
(b^2-4ac)/(2a)^2}
So the equation (1) now could be
rewritten like:
a{[x+b/(2a)]^2 - (b^2-4ac)/(2a)^2} = 0. Or
bt dividing by a which is not equal to zero, we
get:
[x+b/(2a)]^2 - (b^2-4ac)/(2a)^2 = 0.
Or
[x+b/(2a)]^2 = (b^-4ac)/(2a)^2. Taking the square
root,
x+b/(2a) = +sqrt(b^2-4ac)/2a . Or x+b/(2a) =
-sqrt(b^2-4ac)/2a. So we get 2 solutions from the se two
results.
x1 = [-b+sqrt(b^2-4ac)]/(2a)
Or
x2 = [-b-sqrt(b^2-4ac)]/(2a)
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