diketahui jari jari lingkaran X^2 + y^2 + 4x + 6y - (8+b)= 0 adalah 5 nilai b adalah.... pakai cara

[tex]x^2 + y^2 + 4x + 6y - (8+b)= 0 \\ {(x + 2)}^{2} - 4 + {(y + 3)}^{2} - 9 - 8 - b = 0 \\ {(x + 2)}^{2} + {(y + 3)}^{2} = b + 21[/tex]
artinya
[tex] {r}^{2} = b + 21 \\ {5}^{2} = b + 21 \\ b = 4 [/tex]