cho f(x)= 9-x mũ 5 + 4x-2x mũ 3+x mũ 2 – 7 x mũ 4
g(x)= x mũ 5 – 9 +2 x mũ 2 +7 x mũ4+ 2 x mũ 3 – 3x
tính tổng h(x)=f(x)+g(x)
cho f(x)= 9-x mũ 5 + 4x-2x mũ 3+x mũ 2 – 7 x mũ 4 g(x)= x mũ 5 – 9 +2 x mũ 2 +7 x mũ4+ 2 x mũ 3 – 3x tính tổng h(x)=f(x)+g(x)
By Delilah
$Ta$ $có:$ $h(x) = f(x) + g(x)$
$= 9 -x^{5} +4x -2x³ +x² -7x^{4} +x^{5} -9 +2x² +7x^{4} +2x³ -3x$
$= (-x^{5} +x^{5}) + (-7x^{4} +7x^{4}) + (-2x³ +2x³) + (x² +2x²) + (4x -3x) + (9 -9)$
$= 3x² +x$
Tổng h(x) + g(x)
$= ( 9 – x^5 + 4x – 2x^3 + x^2 – 7x^4 ) + ( x^5 – 9 + 2x^2 + 7x^4 +2x^3 – 3x)$
$= 9 – x^5 + 4x – 2x^3 + x^2 – 7x^4 + x^5 – 9 + 2x^2 + 7x^4 +2x^3 – 3x$
$= (-x^5 + x^5) – (7x^4 – 7x^4) – (2x^3 -2x^3) + (x^2 +2x^2 ) (4x – 3x) + (9-9)$
$= 0 – 0 – 0 +3x^2+ x + 0$
$= 3x^2 +x $