Question

X + корень x^2 -9 =21

Answer 1

х+ √(x² -9)=21
 √(x² -9)=21-х
(√(x² -9))²=(21-х)²
x² -9 =21²-42х+х²
42х=441+х²+9-х²
42х=450
х=450/42
х=10 30/42=10 5/7