Factor the following expression:
$5y\left(y-10\right)+4\left(10-y\right)$5y(y−10)+4(10−y).
Simplify $\left(-8x^2-3\right)+\left(-4x^2-8x\right)$(−8x2−3)+(−4x2−8x).
Factor the following expression by taking out the common factor: $3p\left(3q-r+s\right)+20t\left(3q-r+s\right)$3p(3q−r+s)+20t(3q−r+s)
Simplify $\left(-8x^2-1\right)+\left(7x^2+8x\right)$(−8x2−1)+(7x2+8x).