2. Justify each step of the proof.

Conjecture: If 2 (x2 + 5) = 60, then x is 5 or - 5.

1. 2 (x2 + 5) = 60 1.

2. 2x2 + 10 = 60 2.

3. 2x2 = 50 3.

4. x2 = 25 4.

5. x = ±5 5.

Hello,

2 (x²+5) = 60

x²+5=30 (divided teh 2 members by the positive 5 : keep the equality)

x²-25=0 (substract 25 from 2 members)

(x-5) (x+5) = 0 (remarquable product a²-b² = (a+b) (a-b))

x = 5 or x=-5 (a product if null if one at least of its factor is null)