Giải câu 1 bài 3: Đạo hàm của hàm số lượng giác.
a) y=x−15x−2
y′=(x−1)′.(5x−2)−(x−1).(5x−2)′(5x−2)2
=(5x−2)−(x−1).5(5x−2)2
=3(5x−2)2.
b) y=2x+37−3x
y′=(2x+3)′.(7−3x)−(2x+3).(7−3x)′(7−3x)2
=2(7−3x)−(2x+3).(−3)(7−3x)2
=23(7−3x)2.
c) y=x2+2x+33−4x
y′=(x2+2x+3)′.(3−4x)−(x2+2x+3).(3−4x)′(3−4x)2
=(2x+2).(3−4x)−(x2+2x+3).(−4)(3−4x)2
=−2(2x2−3x−9)(3−4x)2.
d) y=x2+7x+3x2−3x
y′=(x2+7x+3)′.(x2−3x)−(x2+7x+3).(x2−3x)′(x2−3x)2
=(2x−7).(x2−3x)−(x2+7x+3).(2x−3)(x2−3x)2
=−10x2−6x+9(x2−3x)2.
