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jimthompson5910 (jim_thompson5910):
Start with the first equation as shown in step 1. In step 2, you'll replace 'y' with '4x-3'. From then on, you get everything to one side and combine like terms.
\[\Large y=-x^2+2x-3\]
\[\Large 4x-3=-x^2+2x-3\]
\[\Large 4x-3+x^2-2x+3=0\]
\[\Large x^2+2x=0\]
I'll let you finish
OpenStudy (song_of_the_sole):
wait so what do i do
jimthompson5910 (jim_thompson5910):
hint: factor
OpenStudy (song_of_the_sole):
im so confused
jimthompson5910 (jim_thompson5910):
try to factor x^2+2x
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OpenStudy (song_of_the_sole):
how do i do that
jimthompson5910 (jim_thompson5910):
what is the common factor of x^2 and 2x?
OpenStudy (song_of_the_sole):
2?
OpenStudy (song_of_the_sole):
am i right?
jimthompson5910 (jim_thompson5910):
think of x^2 as x*x
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jimthompson5910 (jim_thompson5910):
what do x*x and 2*x have in common?
OpenStudy (song_of_the_sole):
so x
OpenStudy (song_of_the_sole):
right?
jimthompson5910 (jim_thompson5910):
yes factor out x to get what?
OpenStudy (song_of_the_sole):
1?
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jimthompson5910 (jim_thompson5910):
x*x+2*x = x*(....)
what goes in the parenthesis?
OpenStudy (song_of_the_sole):
1
jimthompson5910 (jim_thompson5910):
no
jimthompson5910 (jim_thompson5910):
think of distribution but in reverse
OpenStudy (song_of_the_sole):
wait what?
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jimthompson5910 (jim_thompson5910):
for example
x*(x+3) = x*x + 3*x = x^2+3x
so,
x^2+3x = x*(x+3)
OpenStudy (song_of_the_sole):
okay now what
jimthompson5910 (jim_thompson5910):
so what does x^2+2x factor to?
OpenStudy (song_of_the_sole):
im not sure
jimthompson5910 (jim_thompson5910):
use the example I posted
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OpenStudy (song_of_the_sole):
i still dont get it this is all so confusing to me im sorry
jimthompson5910 (jim_thompson5910):
ok one moment
jimthompson5910 (jim_thompson5910):
x times what will get you x^2?
OpenStudy (song_of_the_sole):
x
jimthompson5910 (jim_thompson5910):
x times what will give 2x?
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OpenStudy (song_of_the_sole):
2
jimthompson5910 (jim_thompson5910):
so hopefully you can see how
x^2+2x = x*(x+2)
??
OpenStudy (song_of_the_sole):
ok...?
jimthompson5910 (jim_thompson5910):
if x*(x+2) = 0 then
x = 0
or
x+2 = 0 ----> x = ???
OpenStudy (song_of_the_sole):
2?
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jimthompson5910 (jim_thompson5910):
x+2 = 0 leads to x = ???
it's not x = 2
OpenStudy (song_of_the_sole):
1
jimthompson5910 (jim_thompson5910):
no
jimthompson5910 (jim_thompson5910):
SOMETHING plus 2 = 0
what is that SOMETHING
OpenStudy (song_of_the_sole):
0
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jimthompson5910 (jim_thompson5910):
no
jimthompson5910 (jim_thompson5910):
try to isolate x
OpenStudy (song_of_the_sole):
this is making no sense i dont get it what can be added to 2 to make 0??
jimthompson5910 (jim_thompson5910):
we have x+2 = 0
what must happen to both sides to move the 2 over?
OpenStudy (song_of_the_sole):
subtract
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jimthompson5910 (jim_thompson5910):
subtract what
OpenStudy (song_of_the_sole):
2
jimthompson5910 (jim_thompson5910):
subtract 2 from both sides and you get what?
OpenStudy (song_of_the_sole):
-2
OpenStudy (song_of_the_sole):
ohhh -2+2=0
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OpenStudy (song_of_the_sole):
right?
jimthompson5910 (jim_thompson5910):
yes so either x = 0 or x = -2
OpenStudy (song_of_the_sole):
what about y?
jimthompson5910 (jim_thompson5910):
if x = 0 then y=4x-3 = ???
OpenStudy (song_of_the_sole):
y=4(0)-3
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OpenStudy (song_of_the_sole):
y=-3?
jimthompson5910 (jim_thompson5910):
yes so (0,-3) is one ordered pair solution. There is one more ordered pair solution
jimthompson5910 (jim_thompson5910):
if x = -2, then y=4x-3 = ???
OpenStudy (song_of_the_sole):
y=4(-2)-3
-8-3
-11 y=-11
jimthompson5910 (jim_thompson5910):
yep so the two solutions are `(0,-3)` and `(-2,-11)`
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jimthompson5910 (jim_thompson5910):
If you graph the two equations, the two curves will cross at (0,-3) and (-2,-11)