1) (2x+3)² -(5x-4)(5x+4)=(x+5)²+(3x-1)(7x+2)-(x²-1+1)
2) (1-3x)² -(x-2)(9x+1)=(3x-4)(3x+4)-9(x+3)²
3) (3x+4)(3x-4)-(2x+5)²=(x-5)²+(2x+1)²-(x²-2x)+(x-1)²
4) (x-1)(x+1)-(x-3)²=(3x-5)(3x+5)-(3x+1)²+(x-2)²-x ²
1) (2x+3)² -(5x-4)(5x+4)=(x+5)²+(3x-1)(7x+2)-(x²-1+1)
2) (1-3x)² -(x-2)(9x+1)=(3x-4)(3x+4)-9(x+3)²
3) (3x+4)(3x-4)-(2x+5)²=(x-5)²+(2x+1)²-(x²-2x)+(x-1)²
4) (x-1)(x+1)-(x-3)²=(3x-5)(3x+5)-(3x+1)²+(x-2)²-x ²
Đáp án:
Giải thích các bước giải:
3] (3x+4)(3x-4)-(2x+5)²=(x-5)²+(2x+1)²-(x²-2x)+(x-1)²
9x²-16-4x²-20x-25=x²-10x+25+4x²+4x+1-x²+2x+x²-2x+1
9x²-4x²-20x+10x-4x²-4x+x²-2x-x²+2x=16+25+25+1+1
x²-14x=68
x²-14x-68=0[ vô nghiêm]
4) (x-1)(x+1)-(x-3)²=(3x-5)(3x+5)-(3x+1)²+(x-2)²-x ²
x²-1-x²+6x-9=9x-25-9x²-6x-1+x²-4x+4-x²
6x-10=-9x²-10x-22
6x-10+9x²+10x+22=0
9x²+16x+12=0[vn]