. Tính P(x) + Q (x) ; P(x) -Q(x)
P(x) + Q(x)
= ax2 + bx + c + a'x2 + b'x + c'
= (ax2 + a'x2) + (bx + b'x) +c + c'
= (a + a')x2 + (b + b')x + (c + c')
P(x) - Q(x)
= ax2 + bx + c - (a'x2 + b'x + c')
= ax2 + bx + c - a'x2 - b'x - c'
= (ax2 - a'x2) + (bx - b'x) +c - c'
= (a - a')x2 + (b - b')x + (c - c')