Question

(iii) (3x + 4)(3x - 5)

Answer 1

Answer:

$x_{1}=-\frac{4}{3}\\x_{2}=\frac{5}{3}$

Step-by-step explanation:

$(3x+4)(3x-5)=9x^{2} -15x+12x-20=9x^{2} -3x-20\\\\9x^{2} -3x-20=0\\\\D=b^{2} -4ac=(-3)^{2}-4*9*(-20)=9+720=27^{2} \\\\x_1_,_2=\frac{-b +_- \sqrt{D} }{2a}\\\\x_1=\frac{3-27}{18}=\frac{-24}{18} =-\frac{4}{3}\\\\x_2=\frac{3+27}{18}=\frac{30}{18} =\frac{5}{3}$