Question

What value of c makes the trinomial below a perfect square? x^2+9x+c

Answer 1

Answer:

$(\frac{9}{2})^{2}$

Step-by-step explanation:

In order to calculate this you just have to rememer the quadratic formula:

$a^{2} +2ab+b^{2}$

So we know that 2ab=9x, if we clear that ecuation we can solve the value for b:

$9x=2ab\\b=\frac{9x}{2x} \\b=\frac{9}{2}$

And now we know that b=9/2 and to complete the perfect square we just multiply to the square:

$(\frac{9}{2})^{2}$

Answer 2

81/4 is the answer , use formula (b/2) squared