Answer:
a) ±5
b) ±9
Step-by-step explanation:
In each case, the expression on the left is the square of the expression you're asked to find the value of. Then the value of your expression is the square root of the constant on the right. That square root can be either positive or negative.
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a) a^2 +2ab +b^2 = (a +b)^2 = 25
(a +b) = ±√25 = ±5
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b) a^2 -8ab +16b^2 = (a -4b)^2 = 81
(a -4b) = ±√81 = ±9
