| Step | Hyp | Ref
| Expression |
| 1 | | renegcl.1 |
. 2
⊢ 𝐴 ∈ ℝ |
| 2 | | ax-rnegex 11205 |
. 2
⊢ (𝐴 ∈ ℝ →
∃𝑥 ∈ ℝ
(𝐴 + 𝑥) = 0) |
| 3 | | recn 11224 |
. . . . 5
⊢ (𝑥 ∈ ℝ → 𝑥 ∈
ℂ) |
| 4 | | df-neg 11474 |
. . . . . . 7
⊢ -𝐴 = (0 − 𝐴) |
| 5 | 4 | eqeq1i 2741 |
. . . . . 6
⊢ (-𝐴 = 𝑥 ↔ (0 − 𝐴) = 𝑥) |
| 6 | | 0cn 11232 |
. . . . . . 7
⊢ 0 ∈
ℂ |
| 7 | 1 | recni 11254 |
. . . . . . 7
⊢ 𝐴 ∈ ℂ |
| 8 | | subadd 11490 |
. . . . . . 7
⊢ ((0
∈ ℂ ∧ 𝐴
∈ ℂ ∧ 𝑥
∈ ℂ) → ((0 − 𝐴) = 𝑥 ↔ (𝐴 + 𝑥) = 0)) |
| 9 | 6, 7, 8 | mp3an12 1453 |
. . . . . 6
⊢ (𝑥 ∈ ℂ → ((0
− 𝐴) = 𝑥 ↔ (𝐴 + 𝑥) = 0)) |
| 10 | 5, 9 | bitrid 283 |
. . . . 5
⊢ (𝑥 ∈ ℂ → (-𝐴 = 𝑥 ↔ (𝐴 + 𝑥) = 0)) |
| 11 | 3, 10 | syl 17 |
. . . 4
⊢ (𝑥 ∈ ℝ → (-𝐴 = 𝑥 ↔ (𝐴 + 𝑥) = 0)) |
| 12 | | eleq1a 2830 |
. . . 4
⊢ (𝑥 ∈ ℝ → (-𝐴 = 𝑥 → -𝐴 ∈ ℝ)) |
| 13 | 11, 12 | sylbird 260 |
. . 3
⊢ (𝑥 ∈ ℝ → ((𝐴 + 𝑥) = 0 → -𝐴 ∈ ℝ)) |
| 14 | 13 | rexlimiv 3135 |
. 2
⊢
(∃𝑥 ∈
ℝ (𝐴 + 𝑥) = 0 → -𝐴 ∈ ℝ) |
| 15 | 1, 2, 14 | mp2b 10 |
1
⊢ -𝐴 ∈ ℝ |