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15 votes
Which equation is true?

9x2 - 25 = (3x - 5)(3x - 5)
9x2 - 25 = (3x - 5)(3x + 5)
9x2 – 25 = -(3x + 5)(3x + 5)
9x2 - 25 = -(3x + 5)(3x - 5) ​

User Davekr
by
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1 Answer

14 votes

Answer:


(3x-5)(3x+5)

Explanation:

Difference of squares states that:


a^2-b^2=(a-b)(a+b)

In this case...


a^2=9x^2\\√(a^2)=√(9x^2)\ (take\ the\ square\ root\ of\ both\ sides)\\a=3x


b^2=25\\√(b^2)=√(25)\ (take\ the\ square\ root\ of\ both\ sides)\\b=5

This means that...


9x^2-25=(3x-5)(3x+5)

User Salil
by
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