n(A)=2x+3,n(B)=5x – 1 and n(A∩ B)=x + 1. what can we say about n(A∪ B) ?

Question

n(A)=2x+3,n(B)=5x – 1 and   n(A∩ B)=x + 1. what can we say about n(A∪ B) ?

hartnn · Answer

use the formula that 
$\Large  n(A \cup B) = n(A)+n(B)-n(A∩B)$

hartnn · Answer

just plug in values, what u get ?

hartnn · Answer

@animated.joey , did you get how i got this using the formula ? 
$\Large n (A \cup B) = 2x+3+5x-1 -(x+1)$

can you simplify this ?

anonymous · Answer

sure.i got 6x-1

anonymous · Answer

thank you

hartnn · Answer

3-1-1 = 1 
so wouldn't it be 6x +1 ???

anonymous · Answer

yes my mistake

hartnn · Answer

oh, and since you are new here,
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Have fun learning with Open Study! :)

anonymous · Answer

i have another question.see in the exercise there are given these options : a) 19                               b) 27                              c) 37                                  d) 49                         e) 73 and i should say which one is true for n(A∪ B) .i m i supposed to plug in different values of x in order to get these

anonymous · Answer

oh and thank you :)

hartnn · Answer

any other information is given ?

hartnn · Answer

like total number of elements ?

anonymous · Answer

no nothing more.nevermind i pluged 2 instead of x and got 19.so choice a must be correct

hartnn · Answer

you mean you plugged x =3 and got 19 ?
but if you plug x =6, you get 36
x=8, you get 49

hartnn · Answer

x=6, you get 37***

hartnn · Answer

can you post the screenshot of entire question ?

anonymous · Answer

ok my bad,again.the exercise says which statement CANNOT be true.so if a,c d and e are true then b must be a mistake.

hartnn · Answer

x could be 3, 6, 8 or 12 

notice that 6x+1 means you should have a number which is 1 more than 6x ,
so yeah ,it cannot be 27, as 26 is not multiple of 6
correct , good :)

anonymous · Answer

thank you @hartnn

hartnn · Answer

welcome ^_^

goformit100 · Answer

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