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 07-26-2007 #1 Russell Guest   Posts: n/a algebra 1 help.? how whould i solve using the perfect squares method? if posible can you explain why?13. x^2 â€“ 14x + 49A (-x â€“ 7)(-x â€“ 7)B (x + 7)(x â€“ 7)C (x + 7)(x + 7)D--this one was incorrect---(x â€“ 7)(x + 7)E (x â€“ 7)(x â€“ 7)F This polynomial cannot be factored by using the perfect squares method.16. 4x^4 â€“ 20x^2 + 25A (2x^2 + 5)(2x^2 + 5)B (2x^2 â€“ 5)(2x^2 + 5)---this one is not it. C (-2x^2 â€“ 5)(-2x^2 â€“ 5)D (2x^2 â€“ 5)(2x^2 â€“ 5)E (2x^2 â€“ 5)(-2x^2 + 5)F This polynomial cannot be factored by using the perfect squares method.
 07-26-2007 #2 PsicodÃ©lico Guest   Posts: n/a 13. Answer E16. Answer DI don't speak English, so it is difficult for me to explain why...
 07-26-2007 #3 fofo m Guest   Posts: n/a 1)x^2 â€“ 14x + 49=x^2 -7x -7x + 49=x(x-7)-7(x-7)=(x-7)(x-7)E2)4x^4 â€“ 20x^2 + 25=4x^4 - 10x^2 - 10x^2 + 25=2x^2(2x^2-5) - 5(2x^2-5)=(2x^2-5)(2x^2-5)D
 07-26-2007 #4 Sagar K Guest   Posts: n/a 13: x^2 - 14x + 49If your expression is a perfect square, then your factors will always be of the formAx + B)(Ax + B)this implies that B is not the answer.Ax+B is a factor.Ax+B = 0=> x = -B/AA and B can be either positive or negative. the center term (in this case -14x) is the sum of the two factors. the last term (49) is the product. You should find the two numbers which satisfy these two cases.In this case, lets checkption A: (-x-7) * (-x-7)=> -(x+7) * -(x+7) (taking the -ve sign out)=> (x+7)(x+7)factor: x+7x+7 = 0=> x = -7sum of factors: -7 + -7 = -14 (does not work, we need 14)product of factors: 7*7 = 49 (works)option B: ruled out beforehandoption C: same as Aoption D: not correctoption Ex-7)(x-7)factor: 7product: -7 * -7 = 49 (works)sum = -7 + -7 = -7 -7 = -14 (works)therefore your answer is option E______________________________________________16: 4x^4 - 20x^2 + 25product needed: 25sum needed: -20option B,E is out since the two factors are different.options left: A, C, D, Ftry it out like above and see if that works
 07-26-2007 #5 MAHAAN Guest   Posts: n/a It is E x^2-14x+49x^2-2.x.7+(7)^2(x-7)^2 --------------(As (a+b)^2=a^2-2.a.b+b^2) Ansyou can do it the same way

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