HELP ASAP 10 POINTSS Two mechanical waves bump into each other. The crests of the waves line up with each other and so do the troughs. The result is a wave with a higher amplitude than the original two waves had. What is this called?

Question 1 options:

diffraction

destructive interference

resonance

constructive interference

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

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i do not get it   at all