X2 +14x-15=0 in this equation which add LHS as a perfect square 49. how this 49 will come... please tell about 49??? how this calculated

1 Answer
May 7, 2018

x = 1, and x = - 15

Explanation:

#x^2 + 14x - 15 = 0#
#D = d^2 = b^2 - 4ac = 196 + 60 = 256# --> #d = +- 16#
There are 2 real roots:
#x = - b/(2a) +- d/(2a) = - 14/2 +- 16/2#
#x = - 7 +- 8#
a. x1 = - 7 + 8 = 1
b. x2 = -7 - 8 = - 15
Note.
Because a + b + c = 0, we use the shortcut.
One real root is x1 = 1, and the other is #x2 = c/a = - 15#.