Which of the following expressions should be placed in each set of parentheses below in order to solve the equation by completing the square?
xsquare+6x+(?)=15+(?)
A. 3 over 2
B. 3
C. 6
D. 9
2006-08-11 12:37:22 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
By completing the square, you want the left hand side to be a square of something, i.e.,
x^2 + 6x + ? = (x + *)^2
Don't be fooled byt he Right Hand Side. Since you have 6x, you know * = 3. Then ?=9.
2006-08-11 14:54:43 · answer #1 · answered by Stanyan 3 · 0⤊ 0⤋
D. 9
X^2 + 6x + 9 = 15 + 9
(x+3)^2 = 24.
Consider ax^2 + bx. To complete the square, divide the second term by 2, and square it ---> (b/2)^2.
2006-08-11 20:04:40 · answer #2 · answered by prune 3 · 0⤊ 0⤋
x^2 + 6x + __ = 15 + __
you can divide the middle term by two, then multiply the result by itself to discover the third term.
x^2 + 6x + 9 = 15 + 9
(x + 3)(x + 3) = 24
x + 3 = sqrt 24 or sqrt 4 * 6
x + 3 = plus or minux 2 sqrt 6
x = -3 plus or minus 2 sqrt 6
therefore,
x = -5 plus or minus sqrt 6
x = -1 plus or minus sqrt 6
2006-08-12 00:26:55 · answer #3 · answered by ronw 4 · 0⤊ 0⤋
x^2 + 6x + y = 15 + y
Find half of 6, square it, add to both sides
6/2 = 3
3^2 = 9
ANS : D.) 9
2006-08-11 20:29:07 · answer #4 · answered by Sherman81 6 · 0⤊ 0⤋