i got this problem (1 Viewer)

[fantasy8]

i got this sum and product problem

fpr what value of k will the equation x^2-(k+2)x+(k-4)=0 have:

A) one root eqaul to zero

the next qestion is

given that one root of x^2 - 1.3x - 8.88 =0 is 3.7, find the other

can ya plz show the working out

 

[jemsta]

the x^2-1.3x-8.88=0 just use ur quadratic formula -b±√b^2-4ac/2a
1.3±√1.3^2+4(8.88)/2
then the roots are 3.7 or -2.4 (1dp)

 

[yabby]

well azn ganster answered the 2nd one, i might as well answer the first one

first off a=1 b=(-k+2) c=k-4

if one root is zero, then the product of the roots must be zero
product of roots = c/a
= k-4/1

therefore k-4 = 0
k=4

EDIT: just thought of a even faster way, if an equation has a factor of zero, then it cant have a constant in it, so from there u can go k-4=0, straight away