Question

Solve for x?

Answer 1

\[-4\sqrt{x+9}=20 \]

Answer 2

sqrt(x+9)=-(20/4)

Answer 3

I know how to solve is, I'm just not sure how to get rid of the -4 in the front of the radical.

Answer 4

you need to remove the square from x+9 the way you do that is by squaring both side and you end up with x+9=-(20/4)^2. then solve from there.

Answer 5

yes that 's it

Answer 6

x+9=-20/4)^2. -20/4^2 = -25 then take -25 subtract 9. you will get the answer of x=-34

Answer 7

it's easy to see that this has NO SOLUTION:
(-4)*(-5) = 20
so that means:
\(\large -4\sqrt{x+9}=20 \rightarrow \sqrt{x+9}=-5\)

\(\large \sqrt{x+9}=-5\)
which has no solution because the left side is always positive but the right side is negative

Answer 8

Can't you just square both sides to get rid of the square root, then solve like an equation?

Answer 9

yes you can try to do that... it's one technique you should try to solve it. but why continue when you know this is an impossible equation to solve?

Answer 10

not impossible, no solution...
if you do solve it, the solution is an extraneous solution....

Answer 11

If according to your answer it is √x+9 = -5 then you'd square both sides to have:

x+9 = -25

subtract 9 from both sides

and get -16 as x?

Answer 12

Difficult equation in history

Answer 13

squaring both sides you get positive 25

Answer 14

Oh, that's right thanks

so then x+9=25
subtract 9

then positive 16?

Answer 15

yes... now let's see if the solution of x=16 works....

Answer 16

no no no no =-20

Answer 17

that's wrong

Answer 18

\(\large (-4)(\sqrt{x+9})=20 \)
\(\large (-4)(\sqrt{\color {red}{16}+9})=20 \)
\(\large (-4)(\sqrt{\color {red}{25}})=20 \)
\(\large -4 \cdot 5 = 20 \)
\(\large -20=20 \) ???? not a true statement

Answer 19

so the solution of x=16 is extraneous and not really a solution.

Answer 20

solution \[\left| -4 \right|\]

Answer 21

suggestion hhhh

Answer 22

@AntarAzri , what's the solution?

Answer 23

\[\left| -4 \right|\]

Answer 24

\(\large (-4)(\sqrt{x+9})=20 \)
\(\large (-4)(\sqrt{|-4|+9})=20 \)
\(\large (-4)(\sqrt{4+9})=20 \)
\(\large (-4)(\sqrt{13})=20 \)

x=|-4| doesn't seem to work. That's not a solution.

Answer 25

my oh my I have headaches because of this problem..

Answer 26

no no i dont mean the x
|−4|=4

Answer 27

ok. whatever... my answer stands... NO SOLUTION to the equation:
\(\large (-4)(\sqrt{x+9})=20 \) \)

Answer 28

\[(\left| -4 \right|)(\sqrt{16+9})=20\]

Answer 29

here's wolframs answer:
http://www.wolframalpha.com/input/?i=solve+-4*sqrt%28x%2B9%29%3D20

Answer 30

good

Answer 31

http://www.wolframalpha.com/input/?i=solve+ |%E2%88%924|*sqrt%28x%2B9%29%3D20

Answer 32

?

Answer 33

if u don't understand my answer and expanation maybe someone else can give u a better answer... i will not argue my point further....

Answer 34

Do we agree that it can not be the root of a negative number gives a positive number ?

Answer 35

I'll see what my teacher says when she grades it. Thanks for your time