How to do that.the product of four consecutive even integers is 13440. Using Matlab?
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the product of four consecutive even integers is 13440. Using Matlab's build-in function for operations with polynomials, determine the four integers.
I don't know how to do that
answer is 8 10 12 14
help me please
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Accepted Answer
Jos (10584)
on 20 Sep 2013
One approach is to use brute force:
N = 13440 ;
for k = 2:N
v = k + [0:2:6] ;
p = prod(v) ;
if prod(v)==N,
disp('N is the product of :') ;
disp (v)
break
elseif prod(v) > N
disp('There is no solution')
break
end
end
There are many optimalisations that can be made ...
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More Answers (3)
Image Analyst
on 20 Sep 2013
y = x*(x+2)*(x+4)*(x+6)
= x*(x+2)*(x^2+10X+24)
= x * ( x^3+10x^2+24x + 2x^2+20X+48)
= x^4 + .... and so on.
Then subtract 13440 and use fzero to determine the root. Perhaps that's what he meant.
2 Comments
Image Analyst
on 20 Sep 2013
Visualizing it helps:
x = -20:10;
y = x.*(x+2).*(x+4).*(x+6);
plot(x,y, 'bs-', 'LineWidth', 3);
xl = xlim;
% Plot a horizontal line at y = 13440
line([xl(1), xl(2)], [13440, 13440], ...
'Color', [1,0,0], 'LineWidth', 3);
grid on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
Sean de Wolski
on 20 Sep 2013
Obligatory one-liner:
vals = 2*find(prod(bsxfun(@plus,(2:2:13440).',0:2:6),2)==13440)+[0:2:6]
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