(8+10i)(5 - 8i) my answer is 40 - 14i - 80t
(2i)(-3i)(4i) my answer is -24i
3/6 + 7i my answer is 18/13 + 21/13i
x² + 2x - 3 =0 my answer is {-1,3}
16x² - 48x + 36=49 my answer is {3/2 , 7}
x² + 4x>45 my answer is {x|x<-9 or x >-5
My teacher said to check them again but i don't see nothing wrong
(2i)(-3i)(4i) my answer is -24i
3/6 + 7i my answer is 18/13 + 21/13i
x² + 2x - 3 =0 my answer is {-1,3}
16x² - 48x + 36=49 my answer is {3/2 , 7}
x² + 4x>45 my answer is {x|x<-9 or x >-5
My teacher said to check them again but i don't see nothing wrong
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remember: i*i= -1
for the first problem: I don't know where you got the t in 80...
using FOIL, you get 8*5+8*8i+10i*5+10i*8i (first outer inner last) = 40+64i+50i+80i^2=-40+114i
#2 is correct except you forgot that i*i*i =-i so your answer should be positive.
#3: You need to multiple the i on the top and bottom to combine them. It should be 3/6+(7i*6)/6 which equals (3+42i)/6
#4: it factors down to (x-1)(x+3). you set each of those to zero, so the signs need to be reversed. (Correct answer is {+1, -3})
#5: This one is tricky. Are you sure it's typed in correctly here? You would have to complete the square. I would suggest asking that one in a separate question, as it is difficult and lengthy to explain.
#6: The 9 is correct, the 5 needs to be positive for the same reason as #4
Hope that helps someone. If you have anymore questions, I would suggest asking your teacher when you both have the time.
for the first problem: I don't know where you got the t in 80...
using FOIL, you get 8*5+8*8i+10i*5+10i*8i (first outer inner last) = 40+64i+50i+80i^2=-40+114i
#2 is correct except you forgot that i*i*i =-i so your answer should be positive.
#3: You need to multiple the i on the top and bottom to combine them. It should be 3/6+(7i*6)/6 which equals (3+42i)/6
#4: it factors down to (x-1)(x+3). you set each of those to zero, so the signs need to be reversed. (Correct answer is {+1, -3})
#5: This one is tricky. Are you sure it's typed in correctly here? You would have to complete the square. I would suggest asking that one in a separate question, as it is difficult and lengthy to explain.
#6: The 9 is correct, the 5 needs to be positive for the same reason as #4
Hope that helps someone. If you have anymore questions, I would suggest asking your teacher when you both have the time.