How do I solve the quadratic equation by factoring and setting each factor equal to zero in this problem : 7d(squared) + 18d +8 = 0

Question

the_fizicx99 · Answer

Hm,

7d^2 + 18d + 8 = 0

7 * 8 = 56

14 * 4 = 56
14 + 4 = 18

7d^2 + 14d + 4d + 8 = 0

Factor by grouping, take the first two terms

7d^2 + 14d, they have a GCF in both the coefficient and variable. 7 and d

7d(d + 2) 

4d + 8 only has 4, 4(d + 2)

(7d + 4)(d + 2) = 0

solve for D,

7d + 4 = 0
       -4    -4

7d = -4
/7       /7

D = -4/7 is one solutions

D + 2 = 0
   -2      -2

D = -2 is your other solution. When you substitute in -2 or -4/7 you'll get 0