Question

Please help me quick!
-4 sqrt x+9 =20

Answer 1

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

Answer 2

yea it looks like tht

Answer 3

first one, or second one? they are different

Answer 4

first

Answer 5

divide both sides by -4 to get

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

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

\[\large \sqrt{x+9}=-5\]

Answer 6

can you see what this means?

Answer 7

yes but thats all i have to do to solve?

Answer 8

well you solve for x, but you really don't have to because you can take advantage of one property of square roots

Answer 9

do you see which property I'm referring to?

Answer 10

i dont get it ?

Answer 11

the square root function has a range of nonnegative numbers

Answer 12

what this means is that taking the square root of any positive number (or 0) either gives you 0 or some positive number

Answer 13

so it's not possible to take the square root of some number to get a negative number

Answer 14

so the answer will be the equation ?

Answer 15

not sure what you mean

Answer 16

sqrt x+9 =-5?
i mean like wut do i do after tht?

Answer 17

well the square root has a range of nonnegative numbers, so \[\large \sqrt{x+9}=-5\] is simply not possible (for any x)

Answer 18

which means

\[\large \sqrt{x+9}=-5\]

has no solutions, so by extension the original equation has no solutions

Answer 19

so u cant subtract 9 from both sides to get an answer even if it is no solutions?

Answer 20

no if you have \[\large \sqrt{x+9}=-5\] , your first task is to square both sides first

Answer 21

but there's no need to do it because we know there are no solutions anyway

Answer 22

so why continue if you know 100% there's nothing going to be there

Answer 23

so it would be an extraneous equation?

Answer 24

extraneous solution, yes there would be an extraneous solution because x+9 = 25 does have a solution, but this solution doesn't apply to the original equation

Answer 25

ok i see thanks
:)

Answer 26

yw