SOLUTION: what two numbers added equal -7 and multiplied equal -8

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Question 1121353: what two numbers added equal -7 and multiplied equal -8
Found 3 solutions by ikleyn, math_helper, MathTherapy:
Answer by ikleyn(52787)   (Show Source): You can put this solution on YOUR website!
.
The standard solution is THIS:


x + y = -7     (1)
xy    = -8     (2)


From eq(1) express y = -7-x  and substitute it into eq(2). You will get


x*(-7-x) = 8

x*(7+x) = 8

x^2 + 7x - 8 = 0


 =  = .


Answer.  The numbers are   = 1 and   = -8.


Answer by math_helper(2461)   (Show Source): You can put this solution on YOUR website!
what two numbers added equal -7 and multiplied equal -8
—————————
Let x and y be the two numbers
x+y = -7 —> x = -7-y
xy = -8
Re-write the bottom equation with -7-y substituted for 'x':
(-7-y)y = -8



y=-8 ==> x=1
y=1 ==> x=-8
These are the same answer, as they just swap x and y in a trivial manner.
So the answer is and
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

what two numbers added equal -7 and multiplied equal -8
FACTORS of 8: 

Of these 2 sets of factors, only 8 and 1 can give a SUM or DIFFERENCE of 7, so the 2 factors, 8 and 1 are the 2 factors that are needed.

Now, we just have to place the signs!

Since when they're added and multiplied, they result in - 7 and - 8, respectively, it goes without saying that the 2 factors are:  

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