



 
Hi Chloe, The expansion uses the distributive law of multiplication over addition \[a (b + c) = ab + ac\] or if the multiplication is on the right \[(b + c)a = ba + ca.\] I am going to illustrate with an expression similar to yours, $(2x  7)(3x + 5).$ The first step is to see $(2x  7)$ as $a$ in the first form of the distributive law so the expression is $a(3x + 5)$ where $a = (2x  7).$ Thus
Now you have two instances of the second form of the distributive law, the first with $a = 3x$ and the second with $a = 7.$ Thus step 2 is
Step 3 is to simplify and collect like terms to get
With a little practice you can skip step 2 and go directly from step 1 to step 3. With a little more practice you will be able to go from the original problem directly to step 3. Now try your problem,  


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