Question

Using complete sentences, write an indirect proof proving that if x=30, then 3/4x+5≠20 (3/4 being three over four)

I am awful at proofs and worse at indirect proofs. Can someone help me out? And hopefully explain it?

Answer 1

first step is to define the given hypothesis to make yo understand the question

if x=30, then \(\frac{3}{4}x+5≠20\)
so you have
Q:- x=30
P:- \(\frac{3}{4}x+5≠20\)
and wanna prove if Q then P (Q \(\rightarrow\)P)

Answer 2

fine so far ?
now there is two type of proving:-
type1 : direct proof
type 2 : indirect prove like (contrapositive and contradiction )

Answer 3

Okay I think so. What I understood for the first step was:
To prove if ' x equals 30 ' then ' three fourth x plus five does not equal 20 ' ? x=30 being Q and 3/4x+5≠20 being P?

And okay so 2 types. Direct is proving it to be true correct? or no?

Answer 4

ok , seems u got the point now what proof you wanna me to continue with you contradiction or contrapositive ?

Answer 5

Can you please do? I don't know what I'm trying to do here. What am I explaining and how should I explain it? I kind of understand what is being showed, I just don't know what to do with what Is being showed.

Answer 6

ok ok ^^
since u got what i said above lets prove using contrapositive ,
could you write the truth table of \(Q \rightarrow P\) ?

Answer 7

Erm, somewhat? Again I am a lost cause when it comes to proofs. [Sorry about that. Thats why I need help]

Answer 8

familour with this ?