How do you solve 14n^2 + 24n - 5004 = 014n2+24n5004=0?

2 Answers
Mar 5, 2018

Explanation:

The straightforward way is to use the quadratic formula:
n=(-b+-sqrt(b^2-4ac))/(2a)n=b±b24ac2a
This is for expressions of the form an^2 + bn + can2+bn+c, so in your case a=14, b=24, c=-5004 .

A slightly more complicated way is to reverse foil, trying to factor out your a, b, and c so you can write you equation into
(xn + y)(sn +t) = 0(xn+y)(sn+t)=0, where x, y, s, and t are all numbers. Then you can solve one ()() at a time. But if you have a calculator, the quadratic formula is the best way to go. It'll work every time.

Mar 5, 2018

n = -6/7+-15/7sqrt(78)n=67±15778

Explanation:

Complete the square then use the difference of squares identity to find:

0 = 7/2(14n^2+24n-5004)0=72(14n2+24n5004)

color(white)(0) = 49n^2+84n-175140=49n2+84n17514

color(white)(0) = (7n)^2+2(7n)(6)+36-175500=(7n)2+2(7n)(6)+3617550

color(white)(0) = (7n)^2+2(7n)(6)+6^2-(15^2 * 78)0=(7n)2+2(7n)(6)+62(15278)

color(white)(0) = (7n+6)^2-(15sqrt(78))^20=(7n+6)2(1578)2

color(white)(0) = ((7n+6)-15sqrt(78))((7n+6)+15sqrt(78))0=((7n+6)1578)((7n+6)+1578)

color(white)(0) = (7n+6-15sqrt(78))(7n+6+15sqrt(78))0=(7n+61578)(7n+6+1578)

Hence:

7n = -6+-15sqrt(78)7n=6±1578

So:

n = -6/7+-15/7sqrt(78)n=67±15778