Remember, the exact value cannot involve any rounding or estimates. Now, let's solve this problem. First, we have to translate it into an expression:
√72 - √8 + √128 separate the terms into square roots
√36·2 - √4·2 + √64·2 square root the terms that you can
6√2 - 2√2 + 8√2 they have like radical terms, so combine the terms
6 - 2 + 8 = 12 the coefficients are 12 when combined
12√2 this is the EXACT VALUE of the expression
Hope this helps!
