Rewrite the quadratic function in standard form and give the vertex f(x)=3x^2-6x-9
1 answer:
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Answer:
see explanation
Step-by-step explanation:
Using the sum to product identity
cosx + cosy = 2cos( )cos(
)
Consider left side
(cos5A +cos3A) + (cos15A + cos7A)
= 2cos( )cos(
) + 2cos(
) cos(
)
= 2cos() cos(
) + 2cos(
)cos(
)
= 2cos4AcosA + 2cos11A cos4A ← factor out 2cos4A from both terms
= 2cos4A( cos11A + cosA) ← repeat the process
= 2cos4A( 2cos( )cos(
)
= 2cos4A(2cos()cos(
)
= 2cos4A(2cos6A cos5A)
= 4cos4Acos5Acos6A
= right side , thus verified