The graph shows $y=3^x$ for $-1\le x\le2$. Draw reading guides and use the graph to estimat

Question

The graph shows $y=3^x$ for $-1\le x\le2$. Draw reading guides and use the graph to estimate $x$ when $y=6$.[2] Jun joins $(1,3)$ and $(2,9)$ by a straight line and obtains $x=1.5$. Calculate $3^{1.5}$ to 3 significant figures and use it to check his result.[2] Explain why joining the two points by a straight line does not give the correct graph reading.[1]

Accepted Answer

(a) $x\approx1.6$ (accept 1.55–1.70 with reasonable reading guides). (b) $5.20\ne6$, so the proposed input is not correct. (c) The straight segment does not follow the curve.

Checking an exponential graph estimate

Checking an exponential graph estimate

Solution:

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