senseimichael
New member
- Joined
- Mar 11, 2020
- Messages
- 44
Given that r2-4k2=585 and r+2k=9, find the value of r2+4k2, given that 5rk=125
I worked this out with:
r2+(2k)2=(r+2k)2-2(2kr)
So 5rk=125, which means 2rk=50, which means 4rk=100
So (9)2-100=81-100=-19
I am scratching my head, because while all the steps are correct, how on earth do you get a negative number for something derived from the formula a2+b2? Once you square something, the number becomes positive!
Is there some mistake with my working?
I worked this out with:
r2+(2k)2=(r+2k)2-2(2kr)
So 5rk=125, which means 2rk=50, which means 4rk=100
So (9)2-100=81-100=-19
I am scratching my head, because while all the steps are correct, how on earth do you get a negative number for something derived from the formula a2+b2? Once you square something, the number becomes positive!
Is there some mistake with my working?