x²-8x=768
x²-8x-768=0
(x-32)(x+24)=0
x=32 x=-24
you use 32 because it can be negative
plug in for x
(32)(32-8)(1)=768
32×24=768
this isn't the completing the square method though this is zero product law
If it was priced at $100 and had 30% off, it would cost
($100 - (30% of $100)) =$70.
If there was an additional 20% off, it would cost
($100 - (30% of $100) - (20% of 30% of $100)) = $56.
So the total savings is (100-56)/100=44%.
For $74.99, the answer is the same but the numbers are slightly different,
(74.99 - (30% of 74.99) - (20% of 30% of 74.99))/74.99 = 44%.
