How to factorise 6x^2-11x-10?
Firstly, when we need to factorise an expression like ax2 + bx + c, we should find two numbers m and n such that mn = ac and m+n = b. In this question, a = 6, b = -11, c = -10. So mn = -60 and m+n = -11. Let us use mn = -60 to find the values for m and n. Let write down the possible pairs: 1 and 60, 2 and 30, 3 and 20, 4 and 15, 5 and 12, 6 and 10. In each pair, one of them must be negative. To get m+n = -11, 4 and -15 is the only pair. So we have 6x2 -11x -10 = 6x2 +4x -15x -10 = 2x(3x + 2) - 5(3x + 2) = (2x - 5)(3x + 2).
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