13: x^2 - 14x + 49If your expression is a perfect square, then your factors will always be of the form

Ax + 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 check

ption 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 E

x-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