Lisa solved 3x2 + 1 = 28 as shown. 3x2 + 1 = 28 3x2 = 27 x2 = 9 she concluded that the solutions to this quadratic equation are x = -9 or x = 9. using a complete sentence, explain what mistake she made

Important:  Please use " ^ " to indicate exponentiation:   3x^2 + 1 = 28.

The correct solution follows:  

Subtract 1 from both sides:  3x^2 + 1 = 28  => 3x^2 = 27  => x^2 = 9, and x = plus or minus 3.

This person's solution was OK until the last step, where she mistakenly gave the sqrt of 9 the values -9 and +9.  Again, the correct answers are -3 and +3.

c.   x=2.4cm

step-by-step explanation:

similar triangles are triangles which have the same shape but not the same size. this means their angle measures are equal but their side lengths are not instead they are proportional. to solve, we will set up a proportion and solve.

a proportion is two equal ratios set equal to each other. we form the ratios by finding corresponding sides (sides which match to each other on both triangles by their position). out ratios will be one side of the small triangle over the corresponding side on the big triangle as shown below:

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to solve the proportion, we'll cross multiply by multiplying numerator with denominator across the equal sign.