1. Find the square root of 2 and 8. Add the answers together and multiply this second answer by itself. This should equal 18.

2.(Part 1) Find the square root of 3. Take the answer away from 2 and multiply this second answer by itself. I’ll call that A.
(Part 2) Find the square root of 3. Multiply that by 4 and subtract the answer from 7. I’ll call that b.
If the equation is correct then A should be equal to B.

I suppose it was a test that asking you to insert some math symbols will make the sums correct, right ?
If you try to calculate them with a calculator you will see that the square root of 2 plus the square root of 8, all at the power of 2 give you 18. I suppose the other it’s a the same.

The actual calc is fine except how the hell do you work out a square root without a calculator. I guess back in the dim and distant past they could do it but I haven’t a clue!

David – that is a WOW from me! I will of course be telling D that maths like this is invaluable in many aspects of day-to-day life and as such she should listen carefully to her teachers :)

Sorry for poor english, i’m from Russia
bravo:)) i was afraid that nobody will remebered this school rule. It’s the elementary case of using Isaak Newton(right or no?) binom

I haven’t tried this out yet but here goes:

1. Find the square root of 2 and 8. Add the answers together and multiply this second answer by itself. This should equal 18.

2.(Part 1) Find the square root of 3. Take the answer away from 2 and multiply this second answer by itself. I’ll call that A.

(Part 2) Find the square root of 3. Multiply that by 4 and subtract the answer from 7. I’ll call that b.

If the equation is correct then A should be equal to B.

I’ll go try them and see if they work now :)

I suppose it was a test that asking you to insert some math symbols will make the sums correct, right ?

If you try to calculate them with a calculator you will see that the square root of 2 plus the square root of 8, all at the power of 2 give you 18. I suppose the other it’s a the same.

Maybe i’m missing what is your real question.

Sorry – I should have said: This is part of a NON-calculator maths test.

Yep it works. How close depends on how many decimal places you work to:

1.

(1.4142+2.8284)x(1.4142+2.8284)=18

2.

(2-1.7321)x(2-1.7321)=0.072 (A)

7-(4×1.7321)=0.072 (B)

A=B

:)

“This is part of a NON-calculator maths test. ”

JESUS!!!!

The actual calc is fine except how the hell do you work out a square root without a calculator. I guess back in the dim and distant past they could do it but I haven’t a clue!

(a+b)^2 = a^2 + b^2 + 2ab

(SQR(2)+sqr(8))^2 = 2+8+2*(sqr(2)*sqr(8)), but sqr(8) = 2*sqr(2)

so 2+8+2*(sqr(2)*sqr(8)) = 2+8+2(sqr(2)*2*sqr(2)) = 10+2*(4)

= 18

(a-b)^2 = a^2+b^2-2ab

=> (2-sqr(3))^2 = 4+3-2*2*sqr(3) = 7-4*sqr(3)

David – that is a WOW from me! I will of course be telling D that maths like this is invaluable in many aspects of day-to-day life and as such she should listen carefully to her teachers :)

http://flickr.com/photos/geeksmakemehot/71494695/

First one

#2

http://flickr.com/photos/geeksmakemehot/71496404/

Here is a great site on square root rules…

http://math.usask.ca/emr/roots.html

When you start trying to work out square roots of negative numbers then things start getting interesting :-)

You make my brain hurt.

Sorry for poor english, i’m from Russia

bravo:)) i was afraid that nobody will remebered this school rule. It’s the elementary case of using Isaak Newton(right or no?) binom

Guter Aufstellungsort, ja!

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