math expresion gives two diffrent answers (by hand and using mathomatic / could u plz check what i did wrong)
hello ...
im using mathomatic in my IT studies.
debian:/home/mha13# apt-cache policy mathomatic
mathomatic:
Installed: 12.5.16-1
Candidate: 12.5.16-1
Version table:
*** 12.5.16-1 0
500 http://mirror.hamakor.org.il testing/main Packages
500 http://mirror.hamakor.org.il unstable/main Packages
100 /var/lib/dpkg/status
i was checking my homework and i found something very odd :
in the equsion (from package mathomatic):
(a^2) (18 + (2*(a^2))) 3*a*((a^2) +
a + 15)
#9: y = ------- + --------------------------- -
--------------------
(a - 3) ((a^2) + (3*a) + 9) ((a^3)
- 27)
if run the function simplify ill get y=2 + a
the issue is that if answer this by hand i get other result :
(a^2) (18 + (2*(a^2))) 3*a*((a^2) +
a + 15)
#9: y = ------- + --------------------------- -
--------------------
(a - 3) ((a^2) + (3*a) + 9) ((a^3)
- 27)
using the formula a^3 - b^3= (a-b)(a^2 - ab + b^2)
there for a^3 -27 = ((a^2) + (3*a) + 9) * (a - 3)
(a^2) *((a^2) + (3*a) + 9) + (18 + (2*(a^2)))*(a-3)
- 3*a*((a^2) + a + 15)
=
----------------------------------------------------------------------------------------------------
((a^3) - 27)
the strange issue is that upper expression should be
= a^4 - 3a^2 + 9a^2 + 18a+2a^3 -54 -6a^2 -3a^3 - 3a^2 -45a
= a^4 - a^3 +3a^2 - 27a - 54.
but when i put in mathomatic the expression :
(a^2) *((a^2) + (3*a) + 9) + (18 + (2*(a^2)))*(a-3) - 3*a*((a^2)
+ a + 15)
ill get :
#13: y = ((a^2)*((a^2) + (3*a) + 9)) + ((18 + (2*(a^2)))*(a - 3))
- (3*a*((a^2) + a + 15))
13-> simplify
#13: y = (a^4) + (2*(a^3)) - (27*a) - 54
where did the a^3 went away ?
p.s
i know that it is 6 grade issues but still i can't figure it out ..
Yours Truley
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