giải giúp mình với gấp ạ ksnzkqkzka

`color{#1be01b}{-T}color{#1be01b}{i}color{#1be01b}{t}color{#1be01b}{u}color{#1be01b}{u}color{#1be01b}{u-}color{#1be01c}`

`A_n^2+24C_n^1=140`

`-> (n!)/((n-2)!)+24.(n!)/((n-1)!)=140`

`->n(n-1)+24n=140`

`-> n^2-n+24n=140`

`-> n^2+23n-140=0`

`-> n=5 (TM)` hoặc `n=-28 (KTM)`

`-> (2x-1)^5=C_5^0 .(2x)^5+C_5^1 .(2x)^4.(-1)+C_5^2. (2x)^3.(-1)^2+C_5^3 .(2x)^2.(-1)^3+C_5^4 .(2x)^1.(-1)^4+C_5^5 .(-1)^5=32x^5-80x^4+80x^3-40x^2+10x-1`