Question

One of the solutions to x2 − 2x − 15 = 0 is x = −3. What is the other solution?

x = −5
x = −1
x = 1
x = 5

Answer 1

If you factor the equation you can see what the solutions are.  Two factor a quadratic of the form ax^2+bx+c, find two values which satisfy two conditions...

jk=ac=-15 and j+k=b=-2 so j and k must be -5 and 3 so the factors are:

(x-5)(x+3)

So the other solution is x=5

Answer 2

Solution to an equation is the value of variables satisfying that equation. The other solution to the given quadratic equation is x = 5

How to factorize a quadratic polynomial with single variable?

Quadratic polynomial with single variables are expressible in the form

$ax^2 + bx + c = 0$

where x is the variable and a,b,c are constants.

Its factored form is

$\dfrac{1}{4a^2} \times (2ax -b-\sqrt{b^2 - 4ac})(2ax -b+ \sqrt{b^2 - 4ac})$

The given quadratic equation is $x^2 -2x - 15 = 0$

Factorizing it, we get:

$x^2 - 2x - 15 = 0\\x^2 - 5x + 3x - 15 = 0\\x(x-5) + 3(x-5) = 0\\(x+3)(x-5)= 0\\x -3\\or\\x = 5$

Thus, the second solution of the given equation is x = 5

Thus,

The other solution to the given quadratic equation is x = 5

Learn more about solutions of a  quadratic equation here:

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