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The positive root of t in the following equation, 4t2 + 7...

The positive root of t in the following equation, 4t2 + 7t - 1 = 0, correct to 4 places of decimal, is

A.

1.0622

B.

10.6225

C.

0.1328

D.

0.3218

E.

2.0132

Correct answer is C

4t2+7t1=0

Using a = 4, b = 7, c = -1.

x=b±b24ac2a

= 7±724(4)(1)2(4)

= 7±49+168

= 7±658

= 7±8.06238

The positive answer = 7+8.06238=1.06238

(4 decimal place)