Question

Please help!! question in answers!

Answer 1

\[\frac{ 72 }{ 20-4\sqrt{7} } = 5+\sqrt{7} \]

Answer 2

what is the working for this?

Answer 3

to get from one to the other

Answer 4

probably with conjugate

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

a^2 + ab-ab -b^2

Answer 5

thank you, but what would a and b be?

Answer 6

\[20 .and -4\sqrt{7}\]

Answer 7

thank you

Answer 8

\[20-4\sqrt{7}\]the conjugate will have the changed sign for the square root term b

goal is to get rid of root in the denominator

Answer 9

extending fraction by any term is always allowed\[\frac{ 72 (20+4\sqrt{7}) }{ (20-4\sqrt{7}) (20+4\sqrt{7})} \]

Answer 10

\[\frac{ 1440+288\sqrt{7} }{ (20-4\sqrt{7}) (20+4\sqrt{7})}\]

Answer 11

now, what was stated above with a,b
\[\frac{ 1440+288\sqrt{7} }{ 20^{2}-(4\sqrt{7})^{2}}\]

Answer 12

thank you but It can't be this much working. The original question was \[x^{2}-10x+18 \] and i needed to solve it in simplified surd form. I got the answer \[\frac{ 10\pm \sqrt{28} }{ 2 }\] but I needed to simplify that

Answer 13

what is surd ?

Answer 14

don't worry I think I have found the way to do it

Answer 15

a surd is a number square rooted that can't actually be square rooted e.g \[\sqrt{3} \]

Answer 16

I see, thanks