Answer:
[tex]\large\boxed{-13x^2+34x-29}[/tex]
Step-by-step explanation:
[tex]3(x^2+2x-3)-4(4x^2-7x+5)\qquad\text{use the distributive property}\\\\=(3)(x^2)+(3)(2x)+(3)(-3)+(-4)(4x^2)+(-4)(-7x)+(-4)(5)\\\\=3x^2+6x-9-16x^2+28x-20\qquad\text{combine like terms}\\\\=(3x^2-16x^2)+(6x+28x)+(-9-20)\\\\=-13x^2+34x-29[/tex]