a2 + a - 20=(a-4)(a+5)
a2-9a+20=(a-4)(a-5)
a2 -8a - 20=(a-10)(a+2)
a2-12a+20=(a-10)(a-2)
a2-19a-20=(a+1)(a-20)
ab will be equal to
45
step-by-step explanation: