Chapter 6 - Radical Functions and Rational Exponents - 6-5 Solving Square Root and Other Radical Equations - Practice and Problem-Solving Exercises - Page 395: 9

$x = 16$

$3\sqrt x + 3 = 15$ Subtract $3$ from both sides. $3\sqrt x = 12$ Divide both sides by $3$ $\sqrt x = 4$ Square both sides to remove the square root. $x = 16$ Check for extraneous solutions. Does the answer make the statement true? $3\sqrt {16} + 3 = 15$ $3 \times 4 + 3 = 15$ $12 + 3 = 15$ $15 = 15$ Since the statement is true, we can conclude that $x = 16$.