Evaluating 3x² - 2x + 1 when x = -2

Pre-Algebra · Axiom Academy

EXAMPLE Evaluating 3x^2 - 2x - 1 when x = 2 Substitute carefully — respect the order of operations and keep track of every sign. Evaluate the expression 3x^2 - 2x - 1 when x = 2 . We will substitute step by step, doing the exponent before the multiplication and watching the sign on each term. Nice work! You evaluated 3x^2 - 2x - 1 at x = 2 by substituting and following the order of operations. Substitute everywhere: replace every x with 2 before you compute anything. Exponent before multiplication: work 2^2 = 4 first, then — not . Mind the signs: the expression subtracts 2x and subtracts 1 , so 12 - 4 - 1 , not 12 + 4 - 1 . Result: 3(2)^2 - 2(2) - 1 = 7 . The same careful substitution works for any value of x — plug in, respect the order of operations, and track every sign.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.