Jiayang's answer to wp's Secondary 4 A Maths question.
thank u
but how did u prove the first one ?
the x=r+7
When r=3, x=10. Both parameters are increasing at the same rate => their difference is a constant. So x is always 7 more than r.
i also don’t understand how u got r=7
R=7 is the length of r after 20s. Every second it increases by 0.2cm, after 20s it must've increased by 20x0.2=4cm. Therefore, 3+4=7
i see, thanks for clarifying my doubts
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