Solve using the laws of cosine

13°

Step-by-step explanation:

Cosine formula: a² = b² + c² - 2(b)(c)cos(a)

8² = 21² + 14² - 2(21)(14)cos(x)

64 = 441 + 196 - 588cos(x)

Bring constants to one side

64 = 441 + 196 - 588cos(x)

-441  -441  -196

-196

-573 = -588cos(x)

Divide by the coefficient

-573/-588 = -588cos(x)/-588

cos(x) = 573/588

To find x you need to use arcsin or cos^-1

x = arccos(573/588) = 12.969°

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!

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step-by-step explanation: