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solve by completing the square

t^-8t+9=0

2007-05-23 17:18:25 · 6 answers · asked by annetteXskye 2 in Science & Mathematics Mathematics

6 answers

solving for t in
t² - 8t + 9 = 0
by completing the square.
t² - 8t = -9 by adding -9 to both sides
t² -8t + 16 = 16-9 = 7 by adding 16 to both sides.
(t-4)² = 7 by factoring the left side of the equation.
t-4 = ±√7 by taking the square root of both sides of the equation.
t = 4±√7 by adding 4 to both sides of the equation.

Or, you can use the quadratic formula, x={-b±√[b²- 4ac]}/(2a) but you'll get the same answer. I checked them... both of them... and they're correct. However, the quadratic formula is already set up. You just plug in the values. And it's derived the way we did this problem.

2007-05-23 17:52:54 · answer #1 · answered by gugliamo00 7 · 0 0

I suppose you mean t^2 - 8t + 9 = 0. You wrote the question as t^-8t + 9 = 0. That suggests t to the power -8t, plus 9 = 0

What they want you to do is to rewrite the equation in this form:
A perferct square polynomial + a constant = 0

t^2 - 8t + 9 = 0
(t)^2 - 2(t)(4) + (4)^2 - (4)^2 + 9 = 0
(t - 4)^2 - 16 + 9 = 0
(t - 4)^2 - 7 = 0
(t - 4)^2 = 7
(t - 4) = +/- (sqrt 7)
t = 4 +/- sqrt 7

2007-05-24 00:42:27 · answer #2 · answered by Akilesh - Internet Undertaker 7 · 1 0

Consider the equation :
t^2 - 8t + 9 = 0

Therefore :

t = 4 +- sqrt7

2007-05-24 00:33:22 · answer #3 · answered by Sriram A 2 · 0 0

I am curious. What is the symbol after the first t? All I know is everything before the + needs to equal -9. So solve for t to find a solution equaling -9. Tell me what that symbol is. It's too small.

2007-05-24 00:32:12 · answer #4 · answered by peace seeker 4 · 0 0

t^2-8t+9=0
t^2-8t=-9
{t^2-8t+[(1/2)(-8)]^2}=-9+[(1/...
{(t-4)^2}=-9+16
(t-4)^2=7
t-4=+/-[7^(1/2)]
t=+/-[7^(1/2)]+4
t=6.646 or t=1.354(up to 3 decimal places)

2007-05-24 00:30:48 · answer #5 · answered by jackleynpoll 3 · 0 0

(t^2 - 2*4*t + 4^2) - 7 =0, (t-4)^2 = 7, t-4 = +-sqrt(7),

so t = 4+-sqrt(7)

2007-05-24 00:25:29 · answer #6 · answered by shamu 2 · 0 0

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