Which one?
A. B. C. Or D.

D

Step-by-step explanation:

Given

a² - 1 = 0 ( add 1 to both sides )

a² = 1 ( take the square root of both sides )

a = ± = ± 1

solution is { 1, - 1 } → D

D) {1, -1}

Step-by-step explanation:

Please share the instructions for this problem:  Solve a^2 - 1 = 0, or find the roots of a^2 - 1 = 0.

Answer D is correct.  Try substituting 1 for a, and then -1 for a.  In both cases the given equation is true.

answer: the answer to your question is parallel

∠1≅∠2 by the alternate exterior angles theorem.

step-by-step explanation:

given, a ∥ b and ∠1 ≅ ∠3 .we have to prove that e ∥ f

we know that ∠1≅∠3 and that a || b because they are given. we see that by the alternate exterior angles theorem. therefore, ∠2≅∠3 by the transitive property. so, we can conclude that e || f by the converse alternate exterior angles theorem.

we have to fill the missing statement.

transitivity property states that if a = b and b = c, then a = c.

now, given ∠1≅∠3 and by transitivity property ∠2≅∠3 .

hence, to apply transitivity property one angle must be common which is not in result after applying this property which is ∠1.

the only options in which ∠1 is present are ∠1 and ∠2, ∠1 and ∠4

∠1 and ∠4 is not possible ∵ after applying transitivity we didn't get ∠4.

hence, the missing statement is ∠1≅∠2.

so, ∠1≅∠2 by the alternate exterior angles theorem.