Question

Find the value of c that makes each trinomial a perfect square. Then write the trinomial as a perfect square.

6. x2 – 20x + c
a. c = 64; (x – 8)2 b. c = 20; (x – 10)2 c. c = 100; (x + 10)2 d. c = 100; (x – 10)2

Answer 1

d. c = 100; (x – 10)²

Explanation:

Note that (x+a)²=x²+2ax+a².

In our case, 2a=-20, so 'a' must be -10.

Since c=a², and a=-10, c=(-10²)=100.

Since a=-10, the perfect square is (x – 10)²