Write a Java expression for the following: square root of (b^2 - 4ac)

Math.sqrt(b * b - 4 * a * c)

Math.sqrt() takes the whole expression under the root as its single argument, so everything inside the radical sign goes inside the brackets. Write b^2 as b * b rather than Math.pow(b, 2) — shorter, and it avoids the double return type of pow(). The commonest error is bracketing: Math.sqrt(b * b) - 4 * a * c would take the root of b squared only. When a formula has a bar or a radical spanning several terms, that span becomes one pair of brackets.