SOLUTION: Use foil method to find (5x+4)(4x-1)

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Question 777919: Use foil method to find (5x+4)(4x-1)
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

%285x%2B4%29%284x-1%29 Start with the given expression.


Now let's FOIL the expression.


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


%28highlight%285x%29%2B4%29%28highlight%284x%29-1%29 Multiply the First terms:%285%2Ax%29%2A%284%2Ax%29=20%2Ax%5E2.


%28highlight%285x%29%2B4%29%284x%2Bhighlight%28-1%29%29 Multiply the Outer terms:%285%2Ax%29%2A%28-1%29=-5%2Ax.


%285x%2Bhighlight%284%29%29%28highlight%284x%29-1%29 Multiply the Inner terms:%284%29%2A%284%2Ax%29=16%2Ax.


%285x%2Bhighlight%284%29%29%284x%2Bhighlight%28-1%29%29 Multiply the Last terms:%284%29%2A%28-1%29=-4.


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So we have the terms: 20%2Ax%5E2, -5%2Ax, 16%2Ax, -4


20%2Ax%5E2-5%2Ax%2B16%2Ax-4 Now add every term listed above to make a single expression.


20x%5E2%2B11x-4 Now combine like terms.


So %285x%2B4%29%284x-1%29 FOILs to 20x%5E2%2B11x-4.


In other words, %285x%2B4%29%284x-1%29=20x%5E2%2B11x-4.