# Expand (x + 3y)^5

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The binomial expansion of `(a + b)^n` is `sum_(k=o)^n C(n, k) x^k*y^(n - k)`

Using this the expansion of `(x + 3y)^5` is `x^5 + 15x^4y + 90*x^3*y^2 + 270*x^2*y^3+405*x*y^4+ 243*y^5`

**The binomial expansion of **`(x + 3y)^5 = x^5 + 15x^4y + 90*x^3*y^2 + 270*x^2*y^3+405*x*y^4+ 243*y^5`

**Sources:**