c: A=-6x^2-10x+25x^2-35x+10x-14-19(x^2+8x+16)
=19x^2-35x-14-19x^2-152x-304
=-187x-318
Khi x=2 thì A=-318-187*2=-692
c) \(-2x\left(3x+5\right)+\left(5x+2\right)\left(5x-7\right)-19\left(x+4\right)^2\)
\(=\left(-6x^2-10x\right)+\left(25x^2-35x+10x-14\right)-19\left(x^2+8x+16\right)\)
\(=\left(-6x^2-10x\right)+\left(25x^2-25x-14\right)-\left(19x^2+152x+304\right)\)
\(=-6x^2-10x+25x^2-25x-14-19x^2-152x-304\)
\(=\left(-6x^2+25x^2-19x^2\right)-\left(10x+25x+152x\right)-\left(14+304\right)\)
\(=-187x-318\)
Thay x=2 vào BT ta có:
\(A=-187\cdot2-318=-692\)
Vậy: ...
