1a.
Answer is 8x² - 2x + 8
(x² - 4x + 5) + (7x² + 2x + 3)
The parentheses can go away since this is all addition (associative property of addition)
x² - 4 x + 5 + 7x² + 2x + 3
Combine like terms.
(x^2 + 7x²) + (-4x + 2x) + (5 + 3) = 8x² - 2x + 8
======
1b.
Answer is 5x^2 + 7x - 7
(7x² + 4x - 6) - (2x² - 3x + 1)
Distribute the negative into the right parentheses.
(7x² + 4x - 6) - (2x² - 3x + 1)
= 7x² + 4x - 6 - 2x² + 3x - 1
= (7x² - 2x²) + (4x + 3x) + (-6 - 1)
= 5x^2 + 7x - 7