a) a+2b=b+2a
b)a-b=b-a
c) a/b - b/a
d) a+b=b+a
please explain
thank u
2007-10-18 11:46:47 · 4 answers · asked by Magnun S 3 in Science & Mathematics ➔ Mathematics
d -- that this is always true is the commutative property of addition.
2007-10-18 11:49:31 · answer #1 · answered by Pascal 7 · 1⤊ 0⤋
D is always true because addition is commutative...
If you don't understand, then plug in some numbers for a nd b:
a = 7
b = 10
A) 7+2(10) = 27 =? 10 + 2(7) = 24
27 doesn't equal 24... so NO!
B) 7-10 = 10-7
-3 = 3
This is also NOT true...
C) 7/10 = 10/7
.7 = 1 and 3/7
That is also NOT true...
D) 10+7 = 7+10
17 = 17...
2007-10-18 11:52:39 · answer #2 · answered by sayamiam 6 · 0⤊ 0⤋
You can show something is not always true with one case.
a = 1
b = 2
1 + 2*2 = 2 + 2*1
1 - 2 = 2 - 1
1/2 = 2/1
so D must be true.
(It is also true because of the commutative law of addition.)
2007-10-18 11:57:45 · answer #3 · answered by the1_edge 2 · 0⤊ 0⤋
Know your real number system properties - one of these choices is a carbon copy of the commutative property.
If you aren't sure about that, use two random integers for a and b, and plug them into each choice to see if they work.
2007-10-18 11:50:34 · answer #4 · answered by zelljrc 2 · 0⤊ 0⤋