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Zorluk: OrtaFactoring Polynomials

If the quadratic expression 6x27x56x^2 - 7x - 5 is factored completely into the product of two linear binomials of the form (ax+b)(cx+d)(ax + b)(cx + d), where aa, bb, cc, and dd are integers such that a>c>0a > c > 0, what is the value of the expression adbcad - bc?

Cevap: 13

Cevap

The value of the expression adbcad - bc is 13.

Adım Adım Çözüm

1
Factor the quadratic expression 6x27x56x^2 - 7x - 5.
(3x5)(2x+1)(3x - 5)(2x + 1)
Find two numbers that multiply to 6×(5)=306 \times (-5) = -30 and add to 7-7, which are 10-10 and 33. Rewrite the middle term and factor by grouping: 6x210x+3x5=2x(3x5)+1(3x5)=(3x5)(2x+1)6x^2 - 10x + 3x - 5 = 2x(3x - 5) + 1(3x - 5) = (3x - 5)(2x + 1).
2
Determine the values of the coefficients aa, bb, cc, and dd.
a=3a = 3, b=5b = -5, c=2c = 2, and d=1d = 1
The expression is factored into the form (ax+b)(cx+d)(ax + b)(cx + d) where a>c>0a > c > 0. Comparing the factors (3x5)(3x - 5) and (2x+1)(2x + 1), we see the coefficients of xx are 33 and 22. Since 3>2>03 > 2 > 0, we have a=3a = 3 and c=2c = 2. This leaves b=5b = -5 and d=1d = 1.
3
Calculate the value of adbcad - bc.
13
Substitute a=3a = 3, b=5b = -5, c=2c = 2, and d=1d = 1 into the expression: adbc=(3)(1)(5)(2)=3+10=13ad - bc = (3)(1) - (-5)(2) = 3 + 10 = 13.

Anahtar Kavram

Factoring quadratic polynomials of the form ax2+bx+cax^2 + bx + c with a>1a > 1.
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