Question

So i think you have to solve the equation by completing the square..please i really need help..:/
a^2-10a-39=0

Answer 1

do you know what completing the square is?

Answer 2

Yes i do, i mean we just started this but im still a little hung up on the process

Answer 3

ok, so first, add 39 to both sides, tell me what you get

Answer 4

Its 39?

Answer 5

no, i mean do this: a^2-10a-39+39=39. Simplify that for me

Answer 6

a^2-10a=39

Answer 7

@HaileyD here is a suggestion

\[a ^{2} +13a-3a-39\] = 0

try next ...... :)

Answer 8

right, so now the goal is to get the left side to become a PERFECT SQUARE TRINOMIAL

Answer 9

do you know how to make a^2-10a into a perfect square trinomial?

Answer 10

(b/2)^2? which was (10/2)^2 and i got 25 then i added 25 to both sides and thats where i got lost

Answer 11

GREAT! so add that to both sides, simplify and write what you got

Answer 12

Is it (a-8)^2=64?

Answer 13

no, i want you write the non-factored version

Answer 14

ok, i'll write it: a^2-10a+25=39+25. Simplify that if you can. Tell me if you need help

Answer 15

\[(a ^{2}-13a) + (3a-39)=0\]

\[a(a-13) + 3(a-13) =0\]

\[so , (a+3) (a-13) =o \]
\[\in fact (a+3) =0 Or (a-13) = 0 is must\]
so , answers are ...
a= (-3) Or a= 13.

:)

Answer 16

hey hitswild, dont give direct answers

Answer 17

and your method is incorrect

Answer 18

a^2-10a+25=64?

Answer 19

correct, now you need to factor the left side into a perfect square

Answer 20

\(\large\color{black}{ \displaystyle a^2-10a-39=0 }\)
\(\large\color{black}{ \displaystyle a^2-10a=39 }\)
\(\large\color{black}{ \displaystyle a^2-10a+25=39+25 }\)
\(\large\color{black}{ \displaystyle(a-5)^2=64 }\)
and on...

Answer 21

@Rizags O'oo is that so? I'm sorry

Answer 22

@SolomonZelman has it factored correctly. Can you take it from his last step?

Answer 23

Okay thanks ill see what i get...

Answer 24

I got it a=13,-3

Answer 25

@HaileyD - I'm not familiar with English so I don't have a proper Idea about the meaning of "the equation by completing square" but I'm pretty sure the way I got the answers.. pls check the correctness with your fellows.. And the laast step giver by @SolomonZelman is wrong it must be as "\[(a ^{2}-5^{2}) = \sqrt{64} = 8\]"
\
( And keep in mind that [(a ^{2}-5^{2}) = (a-5) (a+5) \] )

:) good luck

try the best and I feel like I 've given all the steps and answers directly and It mustn't. I had to let you think and try it yourself. :(

Answer 26

I dont know if this means or changes anything but im in common core math and it sucks, but the way @Rizags did it looked more familiar to me