What is the net electric field at x = + 2.0 cm?

[mikep]

Can someone please help me with this question?
Two point charges lie on the x axis. A charge of + 3.5 µC is at the origin, and a charge of -3.5 µC is at x = 10.0 cm. What is the net electric field at x = -2.0 cm? What is the net electric field at x = + 2.0 cm?

for the first one i did
$$k q/r^2$$
$$(9 x 10^9) (3.5 x 10^-6)/(0.02m)^2 = 78750000 N/C$$
$$(9 x 10^9) (-3.5 x 10^-6)/(0.12m)^2 = -2187500$$
$$78750000 - 2187500 = 76562500N/C$$
can someone please tell me what I'm doing wrong?

 

[buddingscientist]

what seems to be the problem?
do the solutions have a different answer?:S

 

[mikep]

yeah when i entered this value in, i got it wrong

 

[christinono]

I just tried the first question, and I got 7656250N/C (to the left). I'm sure that's the answer...

 

[mikep]

how do you get that?