SOLUTION: Find the constant p such that x^2 - 5x - 14x + x^2 + p is the square of a binomial.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Find the constant p such that x^2 - 5x - 14x + x^2 + p is the square of a binomial.      Log On


   



Question 1209247: Find the constant p such that x^2 - 5x - 14x + x^2 + p is the square of a binomial.
Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find the constant p such that x^2 - 5x - 14x + x^2 + p is the square of a binomial.
~~~~~~~~~~~~~~~~~~~~~

Reduce to the standard form quadratic polynomial by combining like terms

    2x^2 - 19x + p.


Present it as a square of a binomial

    2x^2 - 19x + p = (ax+b)^2.


It is the same as

    2x^2 - 19x + p = a^2*x^2 + 2abx + b^2.


Hence,

    2   = a^2,  or  a = sqrt%282%29;

    -19 = 2ab,  or  -19 = 2%2Asqrt%282%29%2Ab,  which gives  b = -19%2F%282%2Asqrt%282%29%29 = -%2819%2Asqrt%282%29%29%2F4;

    p = b^2 = 361%2A2%2F16 = 361%2F8.

Solved.