# maths

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Find a30 -a20 for the AP a, a+d, a+2d, a+3d........

• maths -

an=a+(n-1)d so a30=a+(30-1)d=a+29d
Similarly a20=a+19d
so their difference is; a+29d-(a+19d)=a+29d-a-19d=10d

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