2007-10-30 17:57:50 · 11 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
x^2 +8x + 16 = 81
x^2 +8x - 65 = 0
(x - 5) (x+13) = 0
x= 5; x = -13
2007-10-30 18:01:20 · answer #1 · answered by Anonymous · 1⤊ 1⤋
x^2 + 4x + 4x + 16 - 81 = 0
x^2 + 8x - 65 = 0
(x + 13) ( x - 5)
x = -13 and 5
2007-10-30 18:03:33 · answer #2 · answered by ferdie 2 · 1⤊ 0⤋
(x+4)^2=81
Expanded form: (x+4)(x+4)=81
=x^2+8x+16=81
81-16=65
x^2+8x=65
x=5 (5X5=25+8X5=40; 25+45=65)
Not sure how I got the answer, I just do it in my head automatically.. _ . Sorry.
2007-10-30 18:07:35 · answer #3 · answered by Anonymous · 0⤊ 0⤋
5 or -13
2007-10-30 18:23:30 · answer #4 · answered by jhandu_da 2 · 0⤊ 0⤋
x+4=81^(1/2)
x=9-4
x=5
2007-10-30 18:01:41 · answer #5 · answered by Steve French 3 · 0⤊ 2⤋
x + 4 = ± 9
x = 5 , x = - 13
OR
x² + 8x - 65 = 0
(x - 5)(x + 13) = 0
x = 5 , x = - 13
2007-10-31 03:44:33 · answer #6 · answered by Como 7 · 0⤊ 0⤋
Take the square root, which yields plus or mins 9.
Then subtract 4 from 9, and then -9, and you get 5 and -13. Those are your two answers. :)
2007-10-30 18:04:01 · answer #7 · answered by Anonymous · 0⤊ 0⤋
square root both sides
so
(x+4) = 9
x = 9-4 = 5
2007-10-30 18:01:07 · answer #8 · answered by swtgirl988 2 · 0⤊ 1⤋
Take the square root of both sides.
x+4=positive or negative 9
x=5 or -15
2007-10-30 18:01:26 · answer #9 · answered by Mary 4 · 0⤊ 2⤋
(x+4)^2 = 81
Find the square roots of each side, and solve for x.
x+4 = +9 or -9
I think you can do the rest. :)
2007-10-30 18:01:28 · answer #10 · answered by wibelle37 4 · 1⤊ 1⤋