Question

please help solve ( x - 5)(x + 10) =0 this is a quadratic equation do not know how to work the problem

Answer 1

if a*b = 0, then what is true of a or b?

Answer 2

are you saying 0x5 =0?

Answer 3

in a sense yes. but lets be more precise:

a*b = 0 is true when a=0: 0*b = 0
and when b=0: a*0 = 0
and when both are 0: 0*0 = 0

remember how pointless if seemed to do the zero times tables?

Answer 4

( x - 5)(x + 10) =0 is true when:

x - 5 = 0
or
x + 10 = 0

solve each instance for x

Answer 5

Yes I do...I have been out of school 20 something years and this algebra is killing me I just cannot get it.

Answer 6

it was about 20 years for me too before i tried college

Answer 7

okay

Answer 8

so knowing that either part can be zero, how would we solve the following for x

x - 5 = 0
or
x + 10 = 0

Answer 9

x would be 1 or 5?

Answer 10

then again it could be 0

Answer 11

if its not obvious, we can work the algebra ....

x - 5 = 0 ; add 5 to both sides to get x all by itself
+5 +5
---------
x = 5


x + 10 = 0 ; subtract 10 from both sides to get x all by itself
-10 -10
----------
x = -10

Answer 12

lets test these out

( x - 5)(x + 10) = 0 , let x=5
( 5 - 5)(5 + 10) = 0

0(15) = 0 ; true
---------------------------

( x - 5)(x + 10) = 0 , let x=-10
(-10- 5)(-10+ 10) = 0

-15(0) = 0 ; true

Answer 13

so that is the way I need to work the problem correct?