# How to convolve $u(-t)$ with other signals?

How can I convolve the following $$u(t+1)*u(-t)$$ I know that convolution with $$u(t)$$ gives the integral of a function but what change occurs due to $$u(-t)$$?

In general, convolution of a function $$f(t)$$ with $$u(-t)$$ results in a function $$g(t)$$ defined by the following integral:
$$g(t)=\int_{-\infty}^{\infty}f(\tau)u(\tau-t)d\tau=\int_{t}^{\infty}f(\tau)d\tau\tag{1}$$
In the given example, $$f(t)=u(t+1)$$, so you get
$$g(t)=\int_{t}^{\infty}u(\tau+1)d\tau=\int_{t+1}^{\infty}u(\tau)d\tau\tag{2}$$