Solve the following questions

Question

7d²-14d-21=0

3c²+66c+63=0

6c(c-4)=2(18c+168)

Answer 1

For the first two, find a common factor. In the first, pull a 7 out:

7(d² - 2d - 3) = 0 . Now factor and solve. 

For the third, distribute across the parentheses, gather like terms, and set equal to zero. If there are any common factors, pull them out and factor what is left:

6c(c - 4) = 2 (18c + 168)

6c² - 24c = 36c + 336

6c² - 60c - 336 = 0

6(c² - 10 c - 56) = 0

The rest is left to the student.