Which of the given values of a real number \( a\in\left(\frac{\pi}2;\pi\right) \) makes the equality \( \int\limits_a^{2a} (3\sin x-4x)\,\mathrm{d}x=-6a^2 \) true?
Which of the given values of real numbers \( a \), \( b\in\left(0;\frac{\pi}2\right) \), such as \( a < b \), makes the equality \( \int\limits_a^b \cos x\,\mathrm{d}x=2\cos\frac{\pi}4\cdot\sin\frac{\pi}{12} \) true?
Given a function \( f(x)=ax^4+bx \), find real numbers \( a \) and \( b \), such that \( \int\limits_0^1f(x)\,\mathrm{d}x=27 \) and \( \int\limits_{-1}^0f(x)\,\mathrm{d}x=57 \).
Given a function \( f(x)=ax^6+bx^3+cx+8 \), find real numbers \( a \), \( b \) and \( c \), such that \( \int\limits_0^1f(x)\,\mathrm{d}x=\frac{35}4 \), \( f'(0)=2 \) and \( f'(1)=180 \).