Question

HELP, i need help!!!!!!!!!!!!!!

Answer 1

Answer:

t = 7.46, 0.42

Explanation:

h = 126t - 16t²    [ "h" is height, "t" is time ]

when height is 50 feet

• 126t - 16t² = 50

• -16t² +126t -50 = 0

• 16t² -126t +50 = 0

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$\sf use \ quadratic \ formula : x = \dfrac{ -b \pm \sqrt{b^2 - 4ac}}{2a} \ \ when \ ax^2 + bx + c = 0$

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$\Longrightarrow \sf t = \dfrac{-126\pm \sqrt{126^2-4\left(-16\right)\left(-50\right)}}{2\left(-16\right)}$

$\Longrightarrow \sf t = \dfrac{63\pm\sqrt{3169}}{16}$

$\Longrightarrow \sf t = 7.46, \ 0.42$

Answer 2

Let's find

• h=126t-16t²

Put h=50

• -16t²+126t=50
• -16t²+126t-50=0

Use quadratic formula

$\\ \rm\Rrightarrow t=\dfrac{-126\pm\sqrt{126²-4(-16)(-50)}}{-32}$

$\\ \rm\Rrightarrow t=7.5s,0.4s$