12. Reduction Method
It’s to add or subtract
the corresponding terms of the two equations
to obtain an equation with only one unknow.
13. EXAMPLE: PROCEDURE:
1. Multiplie one or both of the equations for factors
non-zero, so that the coefficients of one of the
variables are equal to or opposite.
2. If the coefficients obtained in step 1 are equal,
subtract member to member the two equations; if
the coefficients are opposite, add member to
member; so we get an equation in one unknown.
3. Solve the equation in a single variable.
4. Replace the solution in one of the two original
equations.
21. The literal systems are those where in
addition to the variables there are other
letters (parameters).
22. Example
Transform the system in canonical form.
2x= 2a-y 2x+y=2a
(a+1)x+ay=2a (a+1)x+ay=2a
For literal system the most used method is Cramer, calculating the determinant D, Dx, Dy.
D= = 2a-(a+1) = 2a-a-1= a-1 Dx= = 2a2 -2a=2a(a-1)
Dy= = 4a -2a(a+1)=4a-2a2 -2a=2a-2a2 =2a(1-a)
2 1
a+1 a
2a 1
2a a
2 2a
a+1 2a
23. ...continuous example
The system is determined if D ≠ 0 ie if a-1≠0 a≠1.
● If a≠1 then
● If a=1 then D=0, Dx=0 and Dy=0 and the system is indeterminated.
x= Dx/D= 2a(a-1)/a-1= 2a
y=Dy/D= 2a(a-1)/a-1= -2a(a-1)/a-1= -2a
x= 2a
y= -2a
25. When a system is fractional?
● Are those systems in which at least one of the equations that compose
it appears the unknown of first degree (x; y) in the denominator.
● Is solved with the methods we have already seen. (eg. the
replacement method; method of comparison; reduction method etc ...),
but it should be the
EXISTENCE CONDITION (E. C.)
steps shall be non-zero
all denominators that contain the unknown
37. Find the value of y will go out and replaced in the other two equations using the
method of substitution
So the coefficient of y of the first equation is equal to 1, derive the value of y
45. Find the value of x in the first equation and substitute in last
46. The system solution is given by the triplet (4; 0 ; 5 ) that simultaneously
solves all of the system equations. The system is therefore DETERMINED .
47. WORK MADE BY THE CLASS 2nd A Afm
OF ITCG “CORINALDESI” - SENIGALLIA (AN) - ITALY
Team 1 - Breccia Martina, Franceschetti Sofia, Pinca Julia Andrea
Team 2 - Valentini Alessia, Esposto Giorgia, Biagetti Elena, Montironi Ilaria, Carletti
Lucia
Team 3 - Fabri Luca, Franceschini Simone, Bernardini Alessio, Urbinelli Riccardo,
Saramuzzi Mirko
Team 4 - Rossi Davide, Ventura Devid, Latini Angelo
Team 5 - Cervasi Michela, Casella Federica, Raccuja Ilaria
Team 6 - Zhang Qiuye , Zhang Ting, Xie Sandro
Team 7 - Trionfetti Sara, Carbonari Gloria, Borgacci Francesca, Avaltroni Alessia