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Question
Simplify the following expressions:
`(5 + sqrt7)(5 - sqrt7)`
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Solution
We know that `(a + b)(a - b) = a^2 - b^2`We will use this property to simplify the expression
`(5 + sqrt7)(5 - sqrt7)`
`:. (5 + sqrt7)(5 - sqrt7) = 5^2 - (sqrt7)^2`
`= 5 xx 5 - sqrt7 xx sqrt7`
`25 - sqrt(7 xx 7)`
`= 25 - (7^2)^(1/2)`
`= 25 - 7^1`
= 18
Hence the value of expression is 18.
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