You should start off by separating the brackets as the squared only applies to one of them. We'll deal with that one first. Write the (2x + 3y)^2 as two separate brackets of (2x+3y). Then multiply the first term of the first bracket by the terms in the second then do the same for the second term and add all of the values you get together. Collect the like terms and put these values you've added together into a bracket, (4x^2+9x^2+12xy) and multiply by the other bracket. To do this multiply the first term, being x, by the terms in the second bracket then do the same for the second term, -4. Add all the values together and collect like terms to give e you the answer.