Question

Two numbers multiplied together give -15.

They add together to give 2.
What are the two numbers?

Answer 1

x=5 or -3

y=-3 or 5

(x,y) =(5,-3) , (-3,5)

Explanation:

Suppose,

Those two numbers are respectively x & y .

now,

Two numbers multiplied together give -15

so, x . y = -15

∴y =-15/x .........(1)

They add together to give 2 .

so, x+y= 2

=> x+(-15/x) = 2 [From equation (1)]

=>x-15/x = 2

=>(x²-15)/x = 2

=>x²-15 = 2x [Multiply both sides by x]

=>x²-2x-15 = 0

=>x²-5x+3x-15 = 0

=>x(x-5)+3(x-5) = 0

=>(x-5) (x+3)=0

therefore,

x=5 or x=-3

If x=5,

y = -15/5 [From equation (1)]

∴y= -3

If x=-3,

y = -15/-3 [From equation (1)]

∴y=5