a) \(2x^2+5x-18\)
\(=2x^2-4x+9x-18\)
\(=2x\left(x-2\right)+9\left(x-2\right)\)
\(=\left(x-2\right)\left(2x+9\right)\)
b) \(4x^2-17x+15\)
\(=4x^2-12x-5x+15\)
\(=4x\left(x-3\right)-5\left(x-3\right)\)
\(=\left(x-3\right)\left(4x-5\right)\)
c) \(-8x^2+10x+7\)
\(=-8x^2-4x+14x+7\)
\(=-4x\left(2x+1\right)+7\left(2x+1\right)\)
\(=\left(2x+1\right)\left(-4x+7\right)\)
d) \(7x^2-30x+8\)
\(=7x^2-28x-2x+8\)
\(=7x\left(x-4\right)-2\left(x-4\right)\)
\(=\left(x-4\right)\left(7x-2\right)\)
e) \(-x^3+11x^2-30x\)
\(=x\left(-x^2+11x-30\right)\)
\(=x\left(-x^2+5x+6x-30\right)\)
\(=x\left[-x\left(x-5\right)+6\left(x-5\right)\right]\)
\(=x\left(x-5\right)\left(-x+6\right)\)
a) 2x\(^2\) + 5x - 18 = 2x\(^2\) + 9x - 4x - 18 = x(2x + 9) - 2(2x + 9) = (x-2)(2x-9)
b) 4x\(^2\) - 17x - 15 = 4x\(^2\) + 20x - 3x - 15 = 4x(x + 5 ) - 3(x + 5) = (4x - 3 )(x + 5)
c) -8x\(^2\) + 10x + 7 = -8x\(^2\) + 14x - 4x + 7 =-2x(4x - 7) - (4x - 7) = (-2x - 1)(4x - 7)
d) 7x\(^2\) - 30x + 8 = 7x\(^2\) + 2x + 28x + 8 = x(7x + 2) + 4(7x + 2) = (x + 4)(7x + 2)
e) - x\(^3\) + 11x\(^2\) - 30x = -x(x\(^2\) - 11x + 30) = -x(x\(^2\) - 5x - 6x + 30) = -x\(\left[x\left(x-5\right)-6\left(x-5\right)\right]\) = -x(x-6)(x-5)
