Question

find r in the following.
17×17=(9+r)(9+r)+(2+r)+(2+r)

Answer 1

Hello,
17×17=(9+r)(9+r)+(2+r)+(2+r);
289=(81+9r+9r+r²)+(4+2r+2r+r²);
289=81+18r+r²+4+4r+r²;
289=85+22r+2r²;
2r²+22r+85-289=0;
2r²+22r-204=0
r²+11r-102=0
Δ=b²-4ac=11²-4×(-102)=121+408=529;
√Δ=√529=23;
r₁,₂=-11±23/2;
r₁=-11-23/2=-34/2=-17
and
r₂=-11+23/2=12/2=6

then
r=-17 or r=6

bye :-)