Question 1063998
m-3 = 4(d-3)
m = 4(d-3)+3
m = 4d-12+3
m = 4d-9
and
m*d = 430 here substitute for m:
(4d-9)*d = 430
d^2*4-9d-430 = 0
Now this equation is in standard quadratic form ax^2+bx+c = 0, so let's work it, the quadratic formula is (-b+/- sqrt(b^2-4ac))/2a:
d = [-(-9)+sqrt((-9)^2-4)*4(-430)]/2*4
d = [-(-9)+sqrt(81+(-16)*(-430))]/2*4
d = [-(-9)+sqrt(81+6880)]/2*4
d = [-(-9)+sqrt6961]/2*4
d = (9+sqrt6961)/8 Now you would repeat the exercise to solve when b is negative.
But We're not looking for a negative number, so let's solve what we've got:
d = 11.55
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Check:
father - 3 = 4(d-3)
f-3 = 4(11.55-3)
f-3 = 34.2
f = 37.2
the problem says f*d = 430
37.2*11.55 = 429.66 round it off, it's 430 Correct
:
John