Question

algebra:
solve x^2+3x
(find 2 solutions)

Answer 1

you need an equation not just an expression. An equation has an = sign in it.

Do you mean
\[ x^2 +3x = 0 \] ?

Answer 2

yes, sorry

Answer 3

do you know how to "factor out" an x ?
there is the "distributive law" x(x+3) can be written as x^2 +3x
factor out the x to undo the "distribution"

in other words,
\[ x^2 +3x = 0 \\ x(x+3)= 0\]

Answer 4

yeah :)

Answer 5

can you find the 2 solutions ?

Answer 6

not really.. x=0/(x+3) ?
or x+3=0 so x=-3?

Answer 7

yes. You can check your answer: try x=0 in
x^2 + 3x

if x=0, we have 0*0 + 3*0 = 0+0 = 0 it works

try x=-3:
-3*-3 + 3*-3= +9 - 9 = 0 it works

Finding the answer uses this idea:

if you have 2 numbers a*b=0
then you know that either a is 0 or b is 0 (or both are 0)

you have x * (x+3) =0
so either x is 0 or (x+3) is 0
you then find either x=0 or x= -3 (and obviously x can't be both 0 and -3 at the same time)

Answer 8

okay, thanks alot, thats really clear!