Square and Cube Root Laws

Mathematics — Second Preparatory

Common mistakes

Writing √(x²) = x always. The correct rule is √(x²) = |x|. If x = −7, then √(x²) = 7.
Writing √(a + b) = √a + √b. For example, √(9 + 16) = 5, while √9 + √16 = 7.
Believing that the square root of a negative number exists among the real numbers. The value of √(−4) is undefined in R.
Forgetting that the cube root of a negative number is negative. Writing ³√(−8) = 2 is wrong; the value is −2.

Square and Cube Root Laws · 6 / 7