Least value of a sin^2 t + b cos^2 t

The same question, asked 2 times: CDS 2 2020*, CDS 1 2021. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
CDS 2 2020
56 $9 \sin^2 \theta + 16 \cos^2 \theta$
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Question 2
CDS 1 2021
46 $3\sin^2 \theta + 4\cos^2 \theta$
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