Question

if x^2+bx+c= (x+e) (x+f) and c is postive and b is negative, what can you say about the sighs of e and f?

Answer 1

e and f are negative

Answer 2

negative

Answer 3

i thought it was postive

Answer 4

just try it with some examples

Answer 5

see the sum of roots of a quadratic is -b/a
a=1 here
if b is -ve then the sum of roots is positive
the product is c/a, and c is +ve, so product is +ve, which means their sign is same
so both roots are positive
now the roots of (x+e)(x+f) are -e and -f, and if these are positive then e and f need to be negative, as - x - = +

Answer 6

x^2 -(e+f)x + (ef)

ef = + number (+e)(+f) OR (-e)(-f)

e+f = - number

(+e)+(+f) = + number; +1+2 = +3

(-e)+(-f) = - number; (-1)+(-2) = -3

Answer 7

ax^2 (+-) bx (+-) c
^ ^
^ tells us to add or subtract
^
tells us the bigger factors sign

Answer 8

x^2 -4x -12
^ ^ subtract factors to get 7
^
the bigger factor is (-)


6(2) = 12
-6+2 = -4

(x-6) (x+2)

Answer 9

umm .... subtract to get 4 .....

Answer 10

so i get a postive?