Algebra · real student question

Evaluate the algebraic expression 2 + 8(x - 2)^3 for x = 6.

Question

Evaluate the algebraic expression

2+8(x2)32+8(x-2)^{3}

for x=6x=6.

Step-by-step solution

  1. Substitute, keeping the brackets exactly as written.

    2+8(62)3.2+8(6-2)^{3}.

    Writing 8628\cdot 6-2 or dropping the parentheses at this point is the most common way to lose the question.

  2. Simplify inside the bracket first. Grouping symbols outrank everything else:

    62=4  2+8(4)3.6-2=4\ \Longrightarrow\ 2+8(4)^{3}.

  3. Apply the exponent before the multiplication. The cube belongs to the bracket only, not to 848\cdot 4:

    43=64  2+8(64).4^{3}=64\ \Longrightarrow\ 2+8(64).

    Cubing 84=328\cdot 4=32 instead would give 3276832768 — a very different answer.

  4. Multiply.

    864=512  2+512.8\cdot 64=512\ \Longrightarrow\ 2+512.

  5. Add last.

    2+512=514.2+512=514.

    The order used — bracket, exponent, multiplication, addition — is exactly the standard hierarchy read left to right through the expression.

Answer

514514

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