Question

Help in completing the square!

Answer 1

\[\large 2v^2 -20v - 7 = 7\]

Answer 2

@TheSmartOne

Answer 3

\[v=5\pm4\sqrt{2}\]

Answer 4

\(\sf\large a^2 -2ab + b^2 = (a-b)^2\)

So we have a = 2
and 2ab = 20

so solve for b

2(2)b = 20

b = >

Answer 5

b = ? *

Answer 6

\[2v^2 - 20v - 14 = 0\]
divided everything by 2
\(v^2 - 10v - 7 = 0\)
\(v^2 - 10v + (-10/2) = 7 + (-10/2)\)
\(v^2 - 10v - 5 = 7 - 5\)
\(\sqrt{v^2 - 10v - 5} = \sqrt{2}\)

I know that i will be getting a very weird answer from the answer key.

Answer 7

is there anything that i am doing wrong?

Answer 8

mhmm

Answer 9

it should be (-10/2)^2

Answer 10

because we have to add b^2 on both sides so we could simplify it :)

Answer 11

but for a previous question, i used the same thing that i am doing now and it matched with the answer key.

Answer 12

but this time it isn't matching the answer key? o_0

Answer 13

Co incidence ,or you match it wrong, it should be square of -5

Answer 14

okay i understand what you're saying. for the last one it was \((2/2)^2 = 1^2 = 1\) that's why i didn't understand that :)

Answer 15

great :)

Answer 16

thanks!

Answer 17

wait a second

Answer 18

ok

Answer 19

nevermind, you got it correct :)

Answer 20

hold on a moment

Answer 21

so i did:
\(v^2 - 10v + 25 = 7 + 25\)
\(v^2 - 10v + 25 = 32\)

\(32\) is not a perfect square but the answer key has whole numbers

Answer 22

@TheSmartOne

Answer 23

so solving that we get

\(\sf\Large v - 5 = \pm\sqrt{32}\)
\(\sf \Large v = 5 \pm \sqrt{32}\)
\(\sf\Large v = 5\pm 4\sqrt{2}\)

what does the answer key say the answer is?

Answer 24

2v^2 - 12v - 7 = 7 {7,-1} <--- answer

Answer 25

do you know my mistake?

Answer 26

maybe we shouldn't have simplified

Answer 27

not sure really mhmm :/

Answer 28

what about this problem
\(6v^2 - 12v - 84 = 6\)

Answer 29

WAIT

Answer 30

\(\color{blue}{\text{Originally Posted by}}\) @calculusxy
2v^2 - 12v - 7 = 7 {7,-1} <--- answer
\(\color{blue}{\text{End of Quote}}\)


we have -12v here

not -20v as you posted

Answer 31

oh wow!

Answer 32

:)