Question

does any one know how to do quadratic equations? and explain them well

Answer 1

"how to do" is a bit vague

Answer 2

Fight vagueness with generality :D
The quadratic formula....

Answer 3

lol okay guys hold on and ill post an equation

Answer 4

x²+7x=0 solve

Answer 5

If you can factor expressions, do so now...

Answer 6

thats the thing terenz i dont even know how to do that

Answer 7

Well, that's a problem... I'm not really good at explaining how to factor... I think @amistre64 is up to the job? :D

Answer 8

factoring is a way to undo a distribution:

a(x+y) = ax+ay

we can undo this by factoring out the common factor of a that we initially distributed

ax + ay = a(x+y)

Answer 9

x²+7x , can you think of a factor that they have in common?

Answer 10

..... is that supposed to be less complicated to understand ? lol you explained it just like my teacher

Answer 11

they have x in common

Answer 12

possibly 7 and 0 maybe

Answer 13

then lets take an x out :)

x (x+7) = 0

now we have to recoginize that 0 times anything is equal to zero; therefore, when x=0 or when x+7 = 0, we have a solution

Answer 14

0 and -7

Answer 15

good, we can dbl chk those

x^2 + 7x = 0 ; let x=0
0^2 + 7(0) = 0 good

x^2 + 7x = 0 ; let x=-7
(-7)^2 + 7(-7) = 0
49 - 49 = 0 ; good

Answer 16

okay so 0 and -7 is the answers?

Answer 17

the key to quadratics is being able to factor them

Answer 18

yes, 0 and -7 produce true results

Answer 19

okay now what about one like x²+8x-48=0

Answer 20

before we go to that one, lets do some background work ... does the term "foil" ring any bells?

Answer 21

yeppp first outside inside last

Answer 22

good, any quadratic comes from the setup:

(x+m)(x+n)

can you "foil" this out for me?

Answer 23

x²+xn+mx+mn

Answer 24

is that all i have to do is foil??

Answer 25

perfect, lets combine the xs like this tho

x^2 + (m+n)x + mn

notice the relationship between the middle and last terms;

the middle is the sum of m and n: m+n
the last is the product of m and n: mn

we use this to determine a suitable m and n for our factorization

Answer 26

x^2 + (8) x + (-48) = 0
x^2 + (m+n)x + (mn) = 0

Answer 27

ok i think i get what you said

Answer 28

what are all the factors that you can think of for -48?

Answer 29

8 4 6

Answer 30

negative and positive

Answer 31

1 48
2 24
-4 +12 <--- this looks promising

Answer 32

12 - 4 = 8
12(-4) = -48

those are what we need right?

Answer 33

-4 and 12 is the answer

Answer 34

not quite, those are the values for m and n in the setup:

(x+m) (x+n) = 0 ; lets use them

(x+12) (x-4) = 0 ; now we can solve for

x+12 = 0
x - 4 = 0

Answer 35

an astute student would recognize the when we find m and n, we just need to reverse the signs for our solution set

12, -4 --> -12, 4

Answer 36

so, the process is:

1) determine factors of last term
2) which set of factors add up to the middle term
3) reverse the signs :)

Answer 37

ok thanks

Answer 38

with a little practice, these will be no problem at all for you :) good luck