Question

(7x²-4x+5).+(3x²+9x-3)-(5x-10)

Answer 1

$(7x^2-4x+5)+(3x^2+9x-3)-(5x-10)\to\\\\ 7x^2-4x+5+3x^2+9x-3-5x+10\to\\\\ 7x^2+3x^2-4x+9x-5x+5-3+10\to\\\\ 10x^2-\not9x+\not9x+12\to\\\\ \large\boxed{10x^2+12}$