What adds to -7 and multiplies to plus 2?

Answer 1

x + y = -7

xy = 2

Solve the second equation for y.

y = 2/x

Substitute the value for y into the first equation.

x + 2/x = -7

Multiply both sides of the equation by x.

x2 + 2 = -7x

Rearrange the equation.

x2 + 7x + 2 = 0

Use the quadratic formula to solve.

x = -b + sq root (b2 - 4ac) / 2a

or x = -b - sq root (b2-4ac) / 2a

a = 1

b = 7

c = 2

x = -7 + sq root (72 - 4*1*2)/2*1=-7 + sq rt (41)/2 = -0.2984

or x = -7 - sq rt (72 - 4*1*2)/2*1 = -6.7016

Use the first equation to solve for y after subtituting in x.

x + y = -7

y = -7 - x

y = -7 - (-0.2984) = -6.7016

or y = -7 - (-6.7016) = -0.2984

So one number is -6.7016 and the other is -0.2984. It doesn't matter which one is x and which is y.

Test the numbers.

-6.7016 + -0.2984 = -7

-6.7016 X -0.2984 = 2

These numbers are rounded to 4 decimal places. If you want to be more or less precise, you could take any number of decimal places that you want.