SOLUTION: Find the product of (3x + 7y)(3x − 7y). A: 9x^2 − 42xy + 49y^2 B: 9x^2 + 42xy + 49y^2 C: 9x^2 − 49y^2 D: 9x^2 + 49y^2 the answer is c right?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find the product of (3x + 7y)(3x − 7y). A: 9x^2 − 42xy + 49y^2 B: 9x^2 + 42xy + 49y^2 C: 9x^2 − 49y^2 D: 9x^2 + 49y^2 the answer is c right?      Log On


   

Question 338081: Find the product of (3x + 7y)(3x − 7y).
A: 9x^2 − 42xy + 49y^2
B: 9x^2 + 42xy + 49y^2
C: 9x^2 − 49y^2
D: 9x^2 + 49y^2
the answer is c right?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
%283x%2B7y%29%283x-7y%29 Start with the given expression.


Now let's FOIL the expression.


Remember, when you FOIL an expression, you follow this procedure:


%28highlight%283x%29%2B7y%29%28highlight%283x%29-7y%29 Multiply the First terms:%283%2Ax%29%2A%283%2Ax%29=9%2Ax%5E2.


%28highlight%283x%29%2B7y%29%283x%2Bhighlight%28-7y%29%29 Multiply the Outer terms:%283%2Ax%29%2A%28-7%2Ay%29=-21%2Ax%2Ay.


%283x%2Bhighlight%287y%29%29%28highlight%283x%29-7y%29 Multiply the Inner terms:%287%2Ay%29%2A%283%2Ax%29=21%2Ax%2Ay.


%283x%2Bhighlight%287y%29%29%283x%2Bhighlight%28-7y%29%29 Multiply the Last terms:%287%2Ay%29%2A%28-7%2Ay%29=-49%2Ay%5E2.


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So we have the terms: 9%2Ax%5E2, -21%2Ax%2Ay, 21%2Ax%2Ay, -49%2Ay%5E2


9%2Ax%5E2-21%2Ax%2Ay%2B21%2Ax%2Ay-49%2Ay%5E2 Now add every term listed above to make a single expression.


9%2Ax%5E2-49%2Ay%5E2 Now combine like terms.


So %283x%2B7y%29%283x-7y%29 FOILs to 9%2Ax%5E2-49%2Ay%5E2.


In other words, %283x%2B7y%29%283x-7y%29=9%2Ax%5E2-49%2Ay%5E2.


So you are correct. The answer is C). Good job.


If you need more help, email me at jim_thompson5910@hotmail.com

Also, feel free to check out my tutoring website.

Jim