## anonymous 5 years ago how do you solve \sqrt{56-r}=r

1. anonymous

56-r=r² => r²+r-56 =0 => delta = 1-4(-56) = 1+ 224=225>0 r1=(-1-sqrt(225))/2=(-1-15)/2=-4 or r2=(-1+sqrt(225))/2=(-1+15)/2=7 r=

2. anonymous

ummm i think its the 1st one

3. anonymous

No, sorry another: $\sqrt{56-r} =r \implies r^2 = 56 - r \implies r^2 + r - 56 = 0$ Therefore (r+8)(r-7) = 0 => r = -8, 7 REMEMBER Squaring can produce spurious roots, but in this case, we check both and they work, so we are fine!

4. anonymous

oh ok thank u