(1)(x²-7x)-(3x²--5-7x)
=x²-7x-3x²+5+7x
=x²-3x²-7x+7x+5
=-2x²+5
(2)(4ab-b²)-2(a²+2ab-b²)
=4ab--b²-2a²-4ab+4b²
=4ab-4ab-b²+4b²-2a²
=3b²-2a²
(1)(x²-7x)-(3x²--5-7x)
=x²-7x-3x²+5+7x
=x²-3x²-7x+7x+5
=-2x²+5
(2)(4ab-b²)-2(a²+2ab-b²)
=4ab--b²-2a²-4ab+4b²
=4ab-4ab-b²+4b²-2a²
=3b²-2a²