A2 初級 美國腔 345 分類 收藏
Okay, so here's another little fun problem
Since the division problem turned out to be so much fun the multiplication and division one. Here's another one that
Somebody pointed out to me
so I think it's
just I don't know let's take a look so
So negative twenty well
That certainly equals negative 20 no arguments there, I think
Let's break up negative 20. I'm gonna break it up on the left
I think I'm gonna write that as 16 minus 36 certainly you still get negative 20 there and
On the right side. I'm gonna write that as 25
minus 45 okay, so
Now I'm gonna rewrite things a little bit more
I'm gonna rewrite 16 is 4 squared and then I'm Gonna rewrite 36 as 4 times 9
On the right side. I'm gonna rewrite 25 as just 5 squared and then I'm Gonna rewrite 45 as
5 times 9 and
Alright, well, I think what I'm gonna. Do now is I'm Gonna add
To both sides and the number that I'm gonna add to both sides is I'm Gonna add 81 over 4
All right, so that's what we've got so far
well actually I think we can factor this now a little bit, so
we can do a couple things here and
You know you can you can check that this all works, so I'm gonna leave the 4 squared alone
We can just rewrite
4/9 pretty easily, I'm Gonna write that as 2 Times 4
times 9 over 2 so I'm just breaking up the 4 over 9 here a little bit and
then I'm Gonna rewrite 81 over 4 as
9 Over 2
Squared on the right side. I'm gonna do the same thing. So we've got 5 squared
What I'm gonna do here is I'm gonna write this as 2 times 5
Times 9 over 2 and then plus 9 over 2 squared
Okay, so you know we're just basically just the Tube and the nine halves would cancel hey give us back our or our nine that
We had up there so all right so far so good well the reason why we do. This is this now factors nicely
this actually factors as 4 minus 9 over 2
Times 4 minus 9 over 2
And the right side is gonna factor as 5 5 minus 9 over 2
Times 5 minus 9 over 2
All right, well
What that tells us is well. We've got 4 minus 9 over 2
squared that equals
5 minus 9 Over 2
Squared and now well that means 4 minus 9 over 2 equals 5 minus
9 over 2 and
well, we could add 9 over 2 to both sides so that tells us that 4 equals 5 and well if we subtract 4 from
both sides
That now tells us that 0 equals 1 so proof complete


證明0 = 1(你能發現錯誤嗎?)

345 分類 收藏
Mumu Lin 發佈於 2020 年 5 月 23 日
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