Question

F(t) = 212 - 61 what the value of t when F(t)= 140 ?

Answer 1

Answer:

$t = -7\ \ \ or\ \ t = 10$

Step-by-step explanation:

Given

$f(t) = 2t^2 - 6t$

Required

Find t, when $f(t) = 140$

Substitute 140 for f(t) in $f(t) = 2t^2 - 6t$

$140 = 2t^2 - 6t$

Divide through by 2

$\frac{140}{2} = \frac{2t^2 - 6t}{2}$

$70 = t^2 - 3t$

$t^2 - 3t = 70$

Subtract 70 from both sides

$t^2 - 3t - 70= 70 - 70$

$t^2 - 3t - 70= 0$

Expand

$t^2 -10t + 7t - 70 = 0$

Factorize:

$t(t - 10) + 7(t - 10) = 0$

$(t + 7)(t - 10) = 0$

Split:

$t + 7 = 0\ \ \ or\ \ t - 10 = 0$

$t = -7\ \ \ or\ \ t = 10$

Hence, the values of t are -7 and 10