Help rearranging this equation

Ive been trying to rearrange this equation for ages and I cant get the answer that is given in the book. I have 0=-4x^2/2+5/2(x-2)^2+16.7. This can be rearranged to give x^2-20x+53.4=0. I cant get anywhere near that, also how would you sove for x from here?

is the first term -(4/2)(x^2) or (-4)(x^(2/2))? In both cases you can easily simplify it

Ive been trying to rearrange this equation for ages and I cant get the answer that is given in the book. I have 0=-4x^2/2+5/2(x-2)^2+16.7. This can be rearranged to give x^2-20x+53.4=0. I cant get anywhere near that, also how would you sove for x from here?