How do you solve #x^2+8x+7=0#?

2 Answers
Aug 15, 2015

Answer:

The solutions are
#color(blue)(x=-7,x=-1#

Explanation:

#x^2+8x+7=0#

The equation is of the form #color(blue)(ax^2+bx+c=0# where:
#a=1, b=8, c=7#

The Discriminant is given by:

#color(blue)(Delta=b^2-4*a*c#
# = (8)^2-(4* 1 * 7)#
# = 64 -28=36#

The solutions are found using the formula
#color(blue)(x=(-b+-sqrtDelta)/(2*a)#

#x = ((-8)+-sqrt(36))/(2*1) = ((-8+-6))/2#

#x=(-8-6)/2, color(blue)(x=-7#

#x=(-8+6)/2, color(blue)(x=-1#

Aug 16, 2015

Answer:

Solve y = x^2 + 8x + 7 = 0

Ans: -1 and -7

Explanation:

Since (a - b + c = 0), use the shortcut. The 2 real roots are (- 1) and (-c/a = - 7).

Reminder of Shortcut :
a. When a + b + c = 0: 2 real roots: (1) and (c/a)
b. When (a - b + c ) = 0: 2 real roots: (-1) and (-c/a)
Remember this Shortcut. It will save you a lot of time and effort.