I'm unable to solve this problem I tried so many times but I didn't get the answer?

Is 15

The tangent of f(x) =−4xe^x at the point (a,f(a)) for (a = 1)
= -8e

　
f(x) = −4x e^x
f(1) = −4e

f'(x) = −4e^x − 4xe^x = −4e^x(x+1)
f'(1) = −8e

Tangent line passes through point (1,−4e) and has slope = −8e

y + 4e = −8e(x − 1)
y = −8ex + 8e − 4e
y = −8ex + 4e

hint:
tangent
y-f(a)=f'(a)(x-a)

--->answer
y=-8ex+4e