SOLUTION: Multiply and simplify: (5 − 2i)(4 + 7i). Write the answer in the form a + bi, where a and b are real numbers. I used FOIL and got the answer: (-14i^2)+27i+20 but ev

Algebra ->  Expressions-with-variables -> SOLUTION: Multiply and simplify: (5 − 2i)(4 + 7i). Write the answer in the form a + bi, where a and b are real numbers. I used FOIL and got the answer: (-14i^2)+27i+20 but ev      Log On


   

Question 891710: Multiply and simplify: (5 − 2i)(4 + 7i).
Write the answer in the form a + bi, where a and b are real numbers.


I used FOIL and got the answer: (-14i^2)+27i+20
but every online calculator is telling me the answer is 34+27i
What is the correct answer?
Found 2 solutions by Tatiana_Stebko, MathTherapy:
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
%285-2i%29%284+%2B+7i%29+
Use FOIL
20%2B35i-8i-14i%5E2
since i%5E2=-1
20%2B27i-14%2A%28-1%29=20%2B27i%2B14=34%2B27i
Answer: 34%2B27i

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
Multiply and simplify: (5 − 2i)(4 + 7i).
Write the answer in the form a + bi, where a and b are real numbers.


I used FOIL and got the answer: (-14i^2)+27i+20
but every online calculator is telling me the answer is 34+27i
What is the correct answer?


i%5E2+=+-1+, so substituting - 1 for i%5E2 in %28-+14i%5E2%29+%2B+27i+%2B+20 results in -+14%28-+1%29+%2B+27i+%2B+20, or 

14 + 27i + 20, which simplifies to: highlight_green%2834+%2B+27i%29, the same answer you've been getting.