What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition, n = 4 to n = 2 of He+ spectrum?

For the transition in He+ spectrum, 1/λ = RZ²[1/n₁² - 1/n₂²]
Substitute values in the above expression.
1/λ = R(2)²[1/2² - 1/4²] = 0.75R. (1)
For the transition in H spectrum, 1/λ = R[1/n₁² - 1/n₂²]. (2)
Both the transitions have the same wavelength.
Hence, from (1) and (2) [1/n₁² - 1/n₂²] = 0.75
Thus, n₁ = 1 and n₂ = 2.