Toán Lớp 8: 11. 2????2 + 5???? − 3 12. ???? + 2????2 − 6 13. 7???? − 6????2 − 2 14. 16???? − 5????2 − 3 15. −7????2 + 11???? + 6

Question

Toán Lớp 8:  11. 2????2 + 5???? − 3 12. ???? + 2????2 − 6 13. 7???? − 6????2 − 2 14. 16???? − 5????2 − 3 15. −7????2 + 11???? + 6

maingoctruc · Answer

Giải đáp: + Lời giải và giải thích chi tiết:    11)   $2x&sup2; + 5x - 3 $   $= 2x&sup2; + 6x - x - 3$   $= 2x(x + 3) - (x-3)$   $= (2x - 1)(x + 3)$   12)   $x + 2x&sup2; - 6$   $= 2x&sup2; + 4x - 3x - 6$   $= 2x(x+2) - 3(x+2)$   $= (2x - 3)(x + 2)$   13)   $7x - 6x&sup2; - 2 $   $= -(6x&sup2; - 7x + 2)$   $= -(6x&sup2; - 3x - 4x + 2)$   $= - (3x(2x - 1) - 2(2x - 1))$   $= - (3x - 2)(2x - 1)$   14)   $16x - 5x&sup2; - 3$   $= -(5x&sup2; - 16x + 3)$   $= - (5x&sup2; - x - 15x - 3)$   $= -(x(5x - 1) - 3(5x - 1))$   $= - (x - 3)(5x - 1)$   15)   $-7x&sup2; + 11x + 6$   $= -(7x&sup2; - 11x - 6)$   $= -(7x&sup2; + 3x - 14x - 6)$   $= -(x(7x + 3) - 2(7x - 3))$   $= -(x-2)(7x + 3)$

thucquyenlan · Answer

11, 2x^2+5x-3   =2x^2-x+6x-3   =x(2x-1)+3(2x-1)   =(2x-1)(x+3)   12, x+2x^2-6   =2x^2-3x+4x-6   =x(2x-3)+2(2x-3)   =(2x-3)(x+2)   13, 7x-6x^2-2   =-6x^2+4x+3x-2   =-2x(3x-2)+(3x-2)   =(3x-2)(-2x+1)   14, 16x-5x^2-3   =-5x^2+15x+x-3   =-5x(x-3)+(x-3)   =(x-3)(-5x+1)   15, -7x^2+11x+6   =-7x^2+14x-3x+6   =-7x(x-2)-3(x-2)   =(x-2)(-7x-3)