SOLUTION: what two numbers multiply to equal -3136 and add up to equal 15?

Question 828420: what two numbers multiply to equal -3136 and add up to equal 15?
Found 3 solutions by stanbon, TimothyLamb, josmiceli:
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
what two numbers multiply to equal -3136 and add up to equal 15?
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Equations:
xy = -3136
x + y = 15
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Substitute for "x" and solve for "y":
(15-y)y = -3136
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y^2 - 15y - 3136 = 0
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(y-64)(y+79) = 0
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If y = 64, x = -79
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Ans: y = 79, x = -64

Answer by TimothyLamb(4379)   (Show Source): You can put this solution on YOUR website!
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xy = -3136
x + y = 15
y = 15 - x
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xy = -3136
x(15 - x) = -3136
15x - xx = -3136
-xx + 15x + 3136 = 0
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the above quadratic equation is in standard form, with a=-1, b=15, and c=3136
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
-1 15 3136
into this solver: https://sooeet.com/math/quadratic-equation-solver.php
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the quadratic has two real roots at:
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x = -49
x = 64
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answer:
x = -49
y = 64
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Solve and graph linear equations:
https://sooeet.com/math/linear-equation-solver.php
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Solve quadratic equations, quadratic formula:
https://sooeet.com/math/quadratic-formula-solver.php
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Solve systems of linear equations up to 6-equations 6-variables:
https://sooeet.com/math/system-of-linear-equations-solver.php
Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!

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By substitution:

Use the quadratic formula

and, also

The numbers are 64 and -49
check:

and

OK

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