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The antineutrino scattering channel ¯νμCH→μ+π−X (nucleon(s)) is analyzed in the incident energy range 1.5 to 10 GeV using the MINERvA detector at Fermilab. Differential cross sections are reported as functions of μ+ momentum and production angle, π− kinetic energy and production angle, and antineutrino energy and squared four-momentum transfer. Distribution shapes are generally reproduced by simulations based on the GENIE, NuWro, and GiBUU event generators, however GENIE (GiBUU) overestimates (underestimates) the cross section normalizations by 8% (10%). Comparisons of data with the GENIE-based reference simulation probe conventional treatments of cross sections and pion intranuclear rescattering. The distribution of nontrack vertex energy is used to decompose the signal sample into reaction categories, and cross sections are determined for the exclusive reactions μ+π−n and μ+π−p. A similar treatment applied to the published MINERvA sample ¯νμCH→μ+π0X[nucleon(s)] has determined the μ+π0n cross section, and the latter is used with σ(π−n) and σ(π−p) to carry out an isospin decomposition of ¯νμ-induced CC(π). The ratio of magnitudes and relative phase for isospin amplitudes A3 and A1 thereby obtained are: R¯ν=0.99±0.19 and ϕ¯ν=93°±7°. Our results are in agreement with bubble chamber measurements made four decades ago.